SAFETY  ENGINEERING 
APPLIED  TO   

SCAFFOLDS 


THE  TRAVELERS  IKSURANCE  COMPANY 

HARTFORD,  CONNECTICUT 


A  TREATISE  ON  SAFETY  ENGINEERING 
AS  APPLIED  TO 


SCAFFOLDS 


THE  TRAVELERS  INSURANCE  COMPANY 

"  HARTFORD,  CONNECTICUT 


This  book  will  be  sent,  postpaid 

to  any  address,  upon  receipt  of  three  dollars.     Address 

THE  TRAVELERS  INSURANCE  COMPANY, 

Hartford,  Connecticut 


Copyright,  1915,  by 

THE  TRAVELERS  INSURANCE   COMPANY, 
Hartford,  Connecticut 


PREFACE 

Scaffolds  are  employed  widely  and  by  many 
different  classes  of  workmen;  but  as  they  are  erected 
for  temporary  use  only,  they  seldom  receive  the 
thoughtful  consideration  that  is  given  to  permanent 
structures.  They  are  badly  designed  and  badly  built, 
as  a  rule,  and  all  too  often  the  materials  that  are  used 
in  them  are  poor  in  quality  and  deficient  in  size  and 
quantity.  In  fact  there  appears  to  be  a  wide-spread 
and  almost  universal  belief  to  the  effect  that  a  scaffold 
is  not  worth  serious  study ;  that  anybody  who  can  drive 
nails  can  build  one  that  will  serve;  and  that  anything 
that  may  happen  to  be  at  hand  is  good  enough  to  go 
into  it.  The  result  is,  that  bricklaying,  carpenter 
work,  painting,  decorating,  and  many  other  operations 
in  which  men  must  work  at  some  considerable  height, 
and  life  and  limb  are  constantly  at  stake,  are  often 
performed  by  the  aid  of  scaffolds  that  are  distinctly 
dangerous,  and  altogether  unfit  for  the  purpose  for 
which  they  were  intended. 

The  very  fact  that  scaffolds  must  be  erected  is 
sometimes  entirely  overlooked  in  making  bids  for 
building  operations  and  other  extensive  work  of  a 
similar  nature,  and  it  is  by  no  means  uncommon  for  a 
sub -contract  or  to  make  no  provision  of  his  own  for  the 
materials  for  his  scaffolds,  but  to  rely  upon  picking  up 
something  about  the  job  that  will  serve  his  purpose. 

These  remarks  are  not  inspired  by  mere  pessi- 
mism. They  are  plain  uncolored  statements  of  facts 


342876 


ii  PREFACE 

that  any  interested  person  can  verify  for  himself  with- 
out the  least  trouble,  and  which  have  become  as 
familiar  to  THE  TRAVELERS  INSURANCE  COMPANY,  in 
the  course  of  its  long  and  extensive  experience  in  com- 
pensation insurance,  as  the  alphabet  or  the  multiplica- 
tion table.  To  see  the  results  of  this  state  of  things  it 
is  only  necessary  to  watch  the  newspapers,  which  are 
continually  reporting  deaths  or  injuries,  through  the 
failure  of  scaffolds  as  a  whole  or  in  some  of  their  parts, 
or  through  the  falling  of  men  because  of  inadequate 
protection  or  no  protection  at  all,  or  through  the  down- 
fall of  tools  or  materials  from  high  places,  upon  work- 
men below,  or  upon  persons  passing  by. 

It  would  be  absurd  to  say  that  scaffolds  are 
universally  bad,  because  quite  a  fair  proportion  of  them 
(an  increasing  proportion,  we  believe)  would  certainly 
be  pronounced  reasonably  safe.  Yet  the  conditions 
that  we  have  outlined  above  are  common  enough  to 
make  it  highly  desirable  to  call  attention  to  them,  and 
to  urge  that  such  methods  be  discontinued,  and  that 
safer  and  more  rational  ones  be  substituted.  Scaf- 
folds are  important  structures,  and  they  should  be 
erected  and  supervised  by  men  who  understand  this 
kind  of  work  thoroughly  well.  The  materials  used 
should  be  first-class  in  quality  and  abundant  in  quan- 
tity, and  every  part  should  be  strong  enough  to  sustain 
any  stress  that  may  be  thrown  upon  it,  without  any 
uncertainty  whatsoever. 

It  is  impossible  to  understand  why  the  general 
subject  of  scaffolding  has  not  been  more  fully  dis- 
cussed in  the  standard  treatises  on  building  and  other 
arts  allied  thereto.  It  is  true  that  there  are  one  or  two 
American  books  which  treat  of  scaffold  problems,  but 


PREFACE  iii 

they  deal  mainly  with  special  scaffolds  which  are  but 
little  used,  and  moreover  they  are  almost  exclusively 
concerned  with  the  efficiency  of  the  workman,  and 
touch  upon  the  question  of  safety  only  briefly  and 
incidentally.  With  these  exceptions  it  is  almost  im- 
possible, in  the  whole  range  of  American  technical 
literature,  to  obtain  detailed  information  respecting 
the  proper  construction  of  scaffolds,  or  the  dangers  that 
are  involved  in  their  use,  or  the  means  that  it  is  advisable 
to  employ,  to  reduce  these  dangers  to  a  minimum. 

The  Building  Trades  Associations  of  Germany  issue 
small  pamphlets  in  which  the  most  essential  points  are 
covered,  and  the  subject  is  also  considered  to  a  very 
limited  extent  in  a  few  of  the  English  books  (as  for 
instance  in  Mitchell's  ''Building  Construction:  Ad- 
vanced Course").  Thatcher's  little  book  is  the  only 
one  we  know  of,  that  is  devoted  exclusively  to  scaf- 
folding. It  is  excellent  so  far  as  it  goes,  but  it  repre- 
sents English  practice  only;  and  as  American  prac- 
tice differs  in  many  respects  from  the  practice  of 
Europe,  foreign  publications  are  necessarily  of  minor 
interest  and  importance  in  this  country.  Suspended 
scaffolds  for  construction  work,  for  example,  such  as 
are  discussed  in  Section  X  of  the  present  volume,  are 
distinctively  American,  and  are  practically  unknown 
in  other  countries. 

The  paucity  of  information  here  noted  in  connec- 
tion with  books,  characterizes  our  various  engineering 
periodicals  also ;  for  while  these  give  occasional  articles 
descriptive  of  newly-designed  scaffolds  or  scaffolds 
that  have  a  "news"  interest  for  some  other  reason,  they 
contain  nothing  respecting  the  commoner  forms  and 
their  dangers. 


iv  PREFACE 

It  might  be  thought  that  the  building  codes  of  our 
larger  cities,  inasmuch  as  they  contain  minute  require- 
ments on  many  points  of  construction,  would  also 
include  specifications  with  regard  to  scaffolds;  but  an 
examination  of  these  codes  shows  that  they  either 
disregard  scaffolds  altogether,  or  treat  them  inade- 
quately and  superficially. 

To  remedy  this  state  of  things,  the  Engineering 
Division  of  THE  TRAVELERS  INSURANCE  COMPANY 
has  prepared  the  present  work,  in  which  various  forms 
of  scaffolding  that  are  commonly  met  with  in  American 
practice  are  illustrated  and  described.  We  have 
treated  the  entire  subject  from  the  standpoint  of 
safety,  and  we  are  confident  that  if  builders  and  others 
will  attend  to  the  points  that  are  discussed  herein, 
there  will  be  a  great  reduction  in  the  number  of  deaths 
and  injuries  that  now  attend  scaffold  work. 

We  believe  that  our  suggestions  are  reasonable 
in  all  cases.  In  addition  to  the  things  that  appear  to 
be  absolutely  essential,  we  have  called  attention  to 
many  others  that  can  be  done  with  advantage;  but 
we  believe  that  we  have  nowhere  been  too  exacting, 
and  we  are  satisfied  that  the  points  upon  which  we 
have  laid  special  stress  will  be  admitted  to  be  of  prime 
importance,  by  all  who  have  given  thoughtful  attention 
to  the  subject. 

The  unsatisfactory  state  of  the  art  of  scaffolding 
in  this  country  is  well  shown  by  the  difficulty  of  obtain- 
ing illustrative  photographs  that  are  satisfactory  in 
all  respects.  A  scaffold  that  shows  excellent  bracing 
may  have  no  guard-rails,  and  one  that  shows  fine, 
large,  straight  poles  may  have  weak  ledgers.  In 
examining  the  engravings  that  we  give,  this  difficulty 


PREFACE  v 

should  be  borne  in  mind.  Illustrations  could  have 
been  "prepared",  in  which  all  conditions  would  have 
been  ideal ;  but  it  was  thought  best  to  give  views  taken 
from  real  scaffolds,  under  actual  working  conditions. 

It  is  impossible,  without  greatly  increasing  the  size 
of  the  book,  to  mention  every  feature  that  tends  to  pro- 
mote safety,  at  every  point  where  it  may  apply.  For 
example,  the  principle  of  overhead  protection  of  men 
on  a  suspended  scaffold  applies  also  to  the  bricklayers' 
pole  scaffold  when  the  work  happens  to  be  done  where 
similar  hazards  exist.  This  should  be  understood,  even 
though  it  is  not  explicitly  mentioned;  and  the  same 
principle  should  be  applied  throughout  the  book.  In 
fact,  the  various  suggestions  that  the  book  contains 
should  be  combined  in  whatever  way  the  conditions 
that  have  to  be  met  may  suggest. 

To  avoid  misunderstanding,  and  to  forestall  any 
criticism  that  might  be  made  because  we  have  not 
dwelt  upon  all  forms  of  builders'  scaffolds  at  a  length 
corresponding  with  their  relative  importance  in  the 
engineering  world,  let  us  point  out  that  the  discussion 
of  each  separate  design  with  the  same  fullness  would 
involve  a  great  deal  of  unnecessary  repetition,  would 
prove  confusing  to  the  reader,  and  would  extend  this 
volume  to  such  dimensions  that  its  usefulness  would 
be  greatly  impaired.  We  have  no  thought  of  giving 
undue  prominence  to  any  special  form  of  scaffold, 
whatsoever,  because  we  stand  only  for  safety;  and  so 
long  as  this  is  assured  beyond  question,  we  do  not  care 
what  particular  type  of  construction  is  adopted.  The 
special  forms  that  we  describe  have  been  chosen  merely 
as  illustrative  of  the  principles  that  are  involved,  and 
it  has  not  appeared  necessary  or  desirable  to  multiply 


VI 


PREFACE 


the  illustrations  further.  It  should  be  borne  in  mind, 
throughout,  that  this  work  is  designed  to  be  merely  a 
treatise  upon  safety  engineering  as  applied  to  scaffold 
work,  and  that  it  does  not  pretend  to  be  encyclopedic. 
In  conclusion  we  beg  to  say  that  the  book  is  based 
mainly  upon  the  results  of  THE  TRAVELERS  INSURANCE 
COMPANY'S  own  experience  and  observation,  obtained 
in  the  course  of  its  regular  work  of  inspection  and 
research,  though  we  desire  to  acknowledge  our  in- 
debtedness to  Mr.  A.  E.  Davidson  of  the  Chesebro- 
Whitman  Company  for  suggestions  on  certain  points, 
and  especially  for  some  of  the  data  in  paragraph  5  7 . 
The  inspection  service  of  THE  TRAVELERS  has  grown 
to  be  enormous,  and  its  staff  includes  men  who  are 
experts  in  every  important  line  of  human  industry. 
A  vast  fund  of  information  has  been  accumulated 
in  this  way,  respecting  the  conditions  that  must  be 
fulfilled  in  order  to  insure  safety  in  industrial  opera- 
tions of  all  kinds,  and  we  are  giving  the  results  of 
our  experience  to  the  general  public  in  a  series  of 
publications  of  this  same  general  nature,  dealing  with 
various  phases  of  the  safety  problem.  We  can  hardly 
doubt  that  this  course  will  lead  to  a  material  improve- 
ment in  existing  standards  of  construction  and  opera- 
tion along  the  many  lines  with  which  we  shall  deal ;  and 
if  this  end  is  accomplished,  and  a  saving  of  life  and  limb 
results,  our  hopes  will  be  realized  and  we  shall  be 
well  repaid. 

THE  TRAVELERS  INSURANCE  COMPANY, 

Hartford,  Connecticut. 


CONTENTS. 

(Paragraph  numbers  are  given  on  the  left,  and  page  numbers  on  the  right.) 

SECTION  I.     REALITY  OF  THE  SCAFFOLD  HAZARD:   .         .         .         .  11 

1.  Few  scaffold  statistics  available,          .          .          .          .          .  11 

2.  Concerning  newspaper  items,     .          .           .          .          .          .  12 

3.  Illustrative  list  of  scaffold  accidents,  ....  13 

4.  Comments  on  the  foregoing  list,          .....  24 

SECTION  II.     SCAFFOLDS  CONSIDERED  GENERALLY:           ...  26 

5.  Forms  and  uses  of  scaffolds,       ......  26 

6.  Scaffolds  for  building, 26 

7.  Pole  scaffolds, 27 

8.  Suspended  scaffolds,  .          .          .          .          .          .          .31 

9.  Outrigger  scaffolds,  ...                    ...  33 

10.  Construction  practice  in  general,         .           .  33 

11.  Carpenters'  outside  stagings,      ......  34 

12.  Painters'  outside  stagings,           ......  34 

13.  Plasterers'  and  decorators'  inside  stagings,  ...  34 

14.  Ladder  scaffolds 35 

15.  Small  hanging  stagings,     .......  35 

16.  Chimney  stagings,    ........  35 

17.  Other  forms  of  scaffolds, 36 

18.  Structures  similar  to  scaffolds:  False  work,  ...  37 

SECTION  III.     BRICKLAYERS' POLE  SCAFFOLD — AMERICAN  PRACTICE:  38 

19.  General  description,  .......  38 

THE  POLES  OR  UPRIGHTS,            ...  38 

20.  Material,  quality,  and  size,         ..... 

21.  Poles  of  extra  strength, 39 

22.  Distance  of  the  poles  from  the  wall,  .....  41 

23.  Spacing  of  the  poles,  parallel  to  the  wall,    .  .          .  41 

24.  Bearing  of  the  pole  at  its  lower  end,  ....  42 

25.  Landslides  or  slips, 44 

26.  Splicing  or  lengthening  the  poles,        .          .  45 


2  CONTENTS 

THE  LEDGERS,           ....  47 

27.  Function  of  the  ledgers,    .......  47 

28.  Material,  size,  and  quality,         ......  48 

29.  Relation  of  the  ledgers  to  the  poles,   .  49 

30.  Vertical  spacing  of  ledgers,         ......  50 

31.  Erecting  the  ledgers,          .......  50 

32.  Nailing,            ....  51 

33.  Splitting  of  ledgers,            .           .                     .           .  52 

34.  Clamps, .53 

THE  PUTLOGS,  .         .  .55 

35.  Function  of  the  putlogs,    .....  55 

36.  Material,  size,  and  quality,         ......  55 

37.  Support  of  the  putlogs,     ....  56 

38.  Security  of  the  putlogs,     ...  58 

39.  Location  of  the  putlogs,    ....  59 

40.  Treatment  of  corners,        ....                     .  60 

41.  Special  forms  of  putlogs,  .......  60 

THE  PLATFORM,            ....  62 

42.  Material,  size,  and  quality  of  platform  planks,     .                     .  62 

43.  Width  of  platform,  ........  63 

44.  Support  of  the  planking  by  the  putlogs,       ....  64 

45.  Treatment  of  corners,        .....  .67 

46.  Shifting  the  platform,        .......  69 

BRACING,      .....  70 

47.  General  considerations,     .......  70 

48.  Bracing  at  window  openings,      .           .                     ...  74 

49.  Shoring, 75 

50.  Spring  stay  braces,  ....                     ...  76 

51.  Caution  in  the  use  of  special  putlogs,           .                              .  79 

52.  Longitudinal  bracing,         ....  80 

OTHER  SAFETY  MEASURES,           ...  82 

53.  Guard-rails,  foot-boards,  etc.,    ....  82 

SECTION  IV.     INDEPENDENT  POLE  SCAFFOLD — AMERICAN  PRACTICE:  83 

54.  Characteristics  of  the  independent  scaffold,           ...  83 

55.  Comparison  with  the  bricklayers'  pole  scaffold,    ...  84 

56.  Bracing,           .........  86 

57.  Design  for  an  independent  pole  scaffold,      ....  90 

58.  Guard-rails,  foot-boards,  etc.,    ......  Q8 

SECTION  V.     LASHED  SCAFFOLDS:  ...                    ...  99 

59.  Characteristics  of  the  lashed  scaffold,           ...  99 

60.  Use  of  round  wood,                       .                                                    .  102 

61.  Tying  the  knots,       .  .  .105 


CONTENTS  3 

62.  Splicing  the  uprights,         .......        107 

63.  Use  of  wire  cords  for  lashing,     .  .          .          .          .          .112 

64.  Use  of  chains,,  .          .          .          .          .          .          .          .114 

65.  Use  of  clamps  and  cramp-irons,           ...  115 

66.  Bracing,  .......                             119 

67.  Guard-rails,  foot-boards,  etc.,    .  .          .          .          .          .119 

SECTION  VI.     OTHER  FORMS  OF  POLE  SCAFFOLDS:  .          .          .       120 

68.  Pole  scaffolds  with  iron  supports,        .....        120 

69.  Ladder  scaffolds,       ...  ....        123 

SECTION  VII.     SPECIAL  SAFETY  FEATURES:     .          .          .          .          .130 

70.  General  considerations,      .......        130 

71.  Guard-rails,     .  .                               .                     .131 

72.  Foot-boards,    .  132 

73.  Wire  netting,  .  .           .           .           .          .          .          .135 

74.  Auxiliary  platforms,  .......        137 

75.  Protection  over  passageways  and  workplaces,       .  .  .        137 

SECTION  VIII.     GENERAL  FEATURES  AND  OPERATIONS:  .          .          .141 

76.  Ladders,  ...                    .          .                                      141 

77.  Runways,         ....  ....        145 

78.  Stairways,        .  .......        149 

79.  Nails, .                    .149 

80.  Dismantling  pole  scaffolds,         ......        152 

SECTION  IX.     BUILDING  WITH  HORSES:           .                   ...       153 

81.  Use  of  horses,  ...                                                          153 

82.  Design  and  condition  of  horses,  .....        154 

83.  The  platforms  on  the  horses,      ......        156 

84.  Use  of  horses  in  tiers,        .          .          .          .          .          .          .157 

85.  Security  of  the  horses,       ....  .160 

86.  Shoring  and  bracing  horse  scaffolds,  .....        163 

87.  Ladders  on  horse  scaffolds,         .          .          .          .          .          .164 

88.  Runways, 165 

89.  Guard-rails  and  foot-boards,      ....  .        165 

90.  Protection  of  workmen  below,   ......        167 

SECTION  X.     SUSPENDED  SCAFFOLDS  FOR  CONSTRUCTION  WORK:       .       168 

91.  Nature  of  the  suspended  scaffold,       .....        168 

92.  Limited  applicability  of  the  suspended  scaffold,  .  .          .        168 

93.  Advantages  of  suspended  scaffolds,     .          .  .  .  .170 

94.  The  two  main  types  of  suspended  scaffolds,          .          .  .173 

95.  Order  of  treatment,  ...                                        .176 

PLATFORM  TYPE  OF  SCAFFOLD  MACHINE,       .          .       176 

96.  Introductory,  .          .           .           .           .           .           .           .176 

97.  Description  of  the  machine,        ......        176 


CONTENTS 

98.  Effect  of  the  breakage  of  a  pawl  or  a  ratchet-wheel,     .          .  179 

99.  Position  of  the  operating  lever  while  at  rest,        .          .          .180 

100.  Possibility  of  disengaging  both  pawls  at  once,      .           .           .  180 

101.  Thrust-outs,  or  projecting  beams,  for  sustaining  the  scaffold,  182 

102.  Anchor  bolts, 183 

103.  Use  of  beam-clamps,          .......  185 

104.  Securing  the  suspension  cables  to  the  thrust-outs,          .           .  187 

105.  Securing  the  suspension  cables  to  the  machines,             .           .  189 

106.  The  putlogs  and  platform,          ......  190 

107.  Safeguard  by  the  pinching  of  the  platform  planks,        .          .  190 

108.  Installing  the  machines,              ...  192 

109.  Dismantling  the  scaffold, 193 

110.  Miscellaneous  safety  features,    ......  194 

OVERHEAD  TYPE  OF  SCAFFOLD  MACHINE,    .          .  194 

111.  General  remarks,      ........  194 

112.  The  thrust-outs, 194 

113.  Description  of  machines,  .......  197 

114.  Distribution  of  stress  in  the  machine,           ....  199 

115.  Effect  of  the  failure  of  a  worm  pin,  by  shearing  or  otherwise,  200 

116.  Riding   of   the   cables  on   the   drums,        ....  201 

117.  Precautions  to  be  observed  in  the  foregoing  operation,    .  204 

118.  Insertion  of  the  worm  pin,          ......  206 

119.  Attachment  of  the  suspension  cables  to  the  drums,       .           .  208 

120.  The  putlogs  and  the  platform, 209 

121.  Installing  and  dismantling  the  machines,     ....  210 

122.  Miscellaneous  safety  features,    .          .          .          .          .          .211 

FEATURES  COMMON  TO  BOTH  TYPES  OF  SUSPENDED  SCAFFOLDS,  212 

123.  Varied  practice  in  the  United  States,  .          .          .          .212 

124.  The  suspension  cables,      .......  212 

125.  Securing  the  ends  of  the  cables  with  fusible  metals,      .          .  213 

126.  The  platform, 217 

127.  Passing  materials  to  the  platform, 219 

128.  Overloading  the  platform, 220 

129.  Safeguard  by  the  pinching  of  the  platform  planks,        .           .  221 

130.  Guard-rails,  foot-boards,  and  side  screens,             .          .          .  224 

131.  Protection  of  scaffold  from  the  fall  of  objects  from  above,     .  229 

132.  Canvas  shields  over  the  platform,       .....  230 

133.  Plank  roofs  for  overhead  protection,             ....  233 

134.  Overhead  protection  by  wire  netting,           ....  238 

135.  One  scaffold  over  another,          .          .          .          .          .          .  240 

136.  Shifting  the  thrust-outs,    .......  242 

137.  Comparison  of  the  overhead  and  platform  scaffolds,     .          .  245 

138.  Cornice  work, 247 

139.  Life  lines  and  safety  belts, 248 

140.  Inspection  of  suspended  scaffolds,       .....  249 


CONTENTS  5 

SECTION  XI.     SCAFFOLDS  OF  OTHER  KINDS: 252 

141.  General  remarks, .252 

142.  Outrigger  scaffolds,            ....  252 

143.  Carpenters'  scaffolds,         .......       258 

144.  Painters'  swinging  scaffolds,       ...  265 

145.  Needle-beam  scaffolds,      .  .272 

146.  Plasterers'  and  decorators'  inside  scaffolds,                     .  .       277 

147.  Miscellaneous  scaffolds,    ...  .283 

SECTION  XII.  STRUCTURES  SIMILAR  TO  SCAFFOLDS:    .    .  .293 

148.  Sidewalk  protection,          .  .       293 

149.  Catch-scaffolds  and  platforms,  ....  .       299 

150.  Material  hoists, .       304 

151.  Arch  centers  and  other  false  work,      ...  .       309 

SECTION  XIII.     GENERAL  COUNSEL:      ...  .312 

152.  Introductory,            .  .       312 

153.  Construction  and  material,         ....  312 

154.  The  human  element,          .          .  315 

155.  Inspection  and  supervision,        .          .  318 

156.  Interference  with  scaffolds,         ...  .        326 

157.  The  load  on  the  platform,           ...  .       330 

158.  Light,     ....  331 

159.  Dismantling  scaffolds,       ....  332 

160.  Scaffolds  serving  several  purposes,      .          .  .       334 

161.  Emergencies,  .........       338 


ILLUSTRATIONS. 

(The  numbers  of  the  illustrations  are  given  on  the  left,  and  the  page  numbers  on  the  right.) 

1.  Safety  scaffolding  (Leipzig  Exposition),  .....  13 

2.  Safety  scaffolding  (Leipzig  Exposition),  .           .          .          .          .  17 

3.  Miscellaneous  scaffolds:   German  practice,        ....  23 

4.  Miscellaneous  scaffolds:   German  practice,        .  28 

5.  Skeleton  of  bricklayers'  pole  scaffold,       .....  30 

6.  Skeleton  of  independent  pole  scaffold,      .....  30 

7.  Miscellaneous  scaffolds:   German  practice,        ....  36 

8.  General  scheme  of  bricklayers'  pole  scaffold,     ....  40 

9.  Scaffold  pole  improperly  secured  at  the  foot,    ....  42 

10.  Scaffold  pole  cut  off  while  in  use,    ......  46 

11.  Special  tool  for  removing  ledgers,    ......  53 

12.  A  form  of  ledger  clamp,          .......  54 

13.  Correct  position  of  putlog,      .          .          .          .          .          .          .  57 

14.  Incorrect  position  of  putlog,  .          .          .          .          .          .          .57 

15.  Special  putlog  for  widely-spaced  bricks,  .....  61 

16.  Special  putlog  for  ordinary  walls,    ......  61 

17.  Usual  arrangement  of  platform  planks,    .....  66 

18.  Another  method  of  laying  the  planks,      .....  66 

19.  Special  treatment  of  planks,  .......  67 

20.  Corner  putlog  in  position,       .......  68 

21.  First  course  of  planks  in  position,   ......  68 

22.  Both  courses  of  planks  in  position,            .....  68 

23.  Buckling  of  the  poles, 72 

24.  Scaffold  falling  away  from  building,          .....  72 

25.  Scaffold  collapsing  parallel  to  wall,           .....  72 

26.  An  excellent  example  of  spring  staying,   .          .          .          .  77 

27.  Guard-rail  and  foot-board  on  Dresden  scaffold,          ...  81 

28.  Independent  pole  scaffold  for  light  work,           ...  85 

29.  Scaffold  stiffened  by  numerous  short  braces,     ....  88 

30.  A  well-braced  American  scaffold,    ......  89 

31.  Design  for  independent  pole  scaffold,        ..... 

32.  An  English  lashed  scaffold,     .          .  100 

33.  First  stage  in  lashing  ledger  to  pole,         .....  102 


8  ILLUSTRATIONS 

34.  Rear  view,  after  tightening  knot,    ......        103 

35.  First  stage  in  securing  ledger,  ......        104 

36.  Finished  knot,  front  view,       .......        105 

37.  Finished  knot,  rear  view,        .......        106 

38.  Lashing  poles  together,  .......        108 

39.  Poles  lashed  together  in  two  places,          .....        110 

40.  Swiss  scaffold,  showing  treatment  of  poles,        .  .  .  .        Ill 

41.  Ends  of  wire-cord  lashings,     .....  .112 

42.  Poles  united  by  wire  cords  and  a  chain,  .          .          .          .          .113 

43.  Chain-tightening  device — slack,       .  .  .  .  .  .114 

44.  Chain-tightening  device — tight,       .  .  .  .  .  .114 

45.  A  cramp-iron,        .  .  .  .  .  .  .  .  .116 

46.  Cramp-irons  supporting  horizontal  brace,          .  .  .117 

47.  Cramp-irons  around  foot  of  scaffold  pole,  .  .  .  .118 

48.  A  bricklayers'  scaffold  with  iron  supports,         .          .          .          .120 

49.  Foot  of  iron  pole,  .          .          .          .          .          .          .          .121 

50.  Iron  brackets  for  bricklayers'  scaffold,      .  .  .  .  .122 

51.  Ladder  scaffold,  for  light  work,        ....  .125 

52.  Another  design  of  ladder  scaffold,   ...  127 

53.  German  ladder  scaffold  of  bricklayers'  type,     ....        128 

54.  All  foot-boards  resting  on  putlogs,  .....        133 

55.  All  foot-boards  resting  on  platform,          .....        133 

56.  Foot-boards  resting  alternately  on  putlogs  and  platform,  .          .        133 

57.  Protective  platform  over  doorway,  ...  .        136 

58.  Support  of  the  platform  shown  in  Fig.  57,         ....        138 

59.  Importance  of  protective  platform,  .....        139 

60.  Approved  method  of  extending  ladders,  .....        143 

61.  Runway  for  independent  pole  scaffold,     .....        146 

62.  Temporary  stairway  used  with  scaffold,  .....        148 

63.  Scaffold  stairways  with  railings,      ......        150 

64.  Scaffold  nails, 151 

65.  A  well-designed  horse,   .          .          .          .          .          .          .          .155 

66.  An  improperly-constructed  horse  scaffold,         .          .          .          .158 

67.  An  unsafe  method  for  raising  a  platform,          ....        159 

68.  A  horse  scaffold  supported  on  outriggers,          .          .          .          .162 

69.  Guard-rail  and  foot-board  on  horse  scaffold,     .          .          .          .166 

70.  The  Clark  scaffold 169 

71.  The  Foster  scaffold, 171 

72.  Illustrating  flexibility  of  suspended  scaffolds,    .          .          .          .173 

73.  The  "Salt  Lake  "scaffold  machine, 175 

74.  "  Patent "  scaffold  machine — platform  type,      .  .  .  .178 

75.  "Patent"  scaffold  machine — platform  type,      ....        179 

76.  Scaffold  platform,  with  platform-type  machines,        .          .          .        181 

77.  Anchoring  of  the  thrust-out,  ......        183 

78.  A  beam  clamp,      .........        185 

79.  Attachment  of  cable  to  thrust-out,  .  .        187 


ILLUSTRATIONS  9 

80.  Spacing  the  channel  irons,      .....  195 

81.  A  special  method  for  securing  thrust-outs,         .          .  196 

82.  An  overhead-type  machine,    ....  197 

83.  The  "riding"  of  the  cables,    .......  202 

84.  Improper  handling  of  overhead  machine,           ....  207 

85.  Hook  for  holding  scaffold  near  wall,         .          .          .          .          .217 

86.  Steel  strap  for  inclosing  platform  planks,  .  .          .  .221 

87.  Wrong  position  of  steel  strap,          .          .          .          .          .          .  222 

88.  Correct  position  of  steel  strap,         ...                    .  222 

89.  Wire  netting  for  scaffold  protection,         .          .          .          .          .227 

90.  Overhead  shield  of  canvas,     .          .          .          .          .          .          .231 

91.  Overhead  shield  of  planking, 234 

92.  Double-platform  scaffold  of  platform  type,       ....  236 

93.  Overhead  protection  of  wire  netting,        .....  239 

94.  Two  scaffolds,  one  above  the  other,          .....  241 

95.  The  "  Perfect "  scaffold  machine, 246 

96.  Supports  of  an  outrigger  scaffold  (Munich),      ....  254 

97.  Framework  scaffold  supported  by  outriggers,    ....  256 

98.  A  well-constructed  outrigger  scaffold,       .....  257 

99.  A  carpenters' bracket  or  "jack"     ......  259 

100.  "Blind  trap"  on  a  carpenters' scaffold,    .....  261 

101.  An  approved  form  of  painters'  hanger,    .....  266 

102.  103,  and  104.     Hitch  for  securing  a  painters' scaffold,          .          .  267 

105.  Double  era wling-board  or  "chicken-ladder, "    ....  271 

106.  The  "scaffold  hitch," 273 

107.  Ladders  and  scaffolds  for  interior  work,  .....  278 

108.  Interior  pole  scaffold,     ........  280 

109.  Design  for  a  plasterers'  interior  scaffold,            ....  281 

110.  Portable  scaffold  for  light  work, 284 

111.  Fixed  pole  scaffold  for  light  work,  ......  286 

112.  Boatswain's  chair, 288 

113.  Another  form  of  boatswain's  chair,            ......  289 

114.  A  boatswain's  chair  on  a  flagstaff,  ......  291 

115.  A  well-designed  sidewalk  shed, 294 

116.  Ornamental  sidewalk  shed  in  New  York  City,            .          .          .  296 

117.  A  very  artistic  sidewalk  shed,          ......  297 

118.  An  exceedingly  ornate  sidewalk  shed,       .....  298 

119.  Catch-scaffolds  for  protecting  sidewalks,  .          .          .          .300 

120.  Catch-scaffolds  on  the  Woolworth  Building,      .          .          .          .302 

121.  One  of  the  platforms  of  Fig.  120,    ...  .303 

122.  A  pair  of  material  hoists,        .......  305 

123.  A  German  material  hoist,       .......  308 

124.  False  work  for  supporting  an  arch,           ...                    .  310 

125.  An  example  of  carelessness,    .......  319 

126.  A  dangerous  needle-beam  scaffold,            ...                    .  320 

127.  Remains  of  a  wrecked  horse  scaffold,       .....  329 


SCAFFOLDS 


I.    REALITY  OF  THE  SCAFFOLD  HAZARD. 

1.  Few  Statistics  Available.  Scaffolds  having 
hitherto  received  so  little  attention,  it  appears  desirable 
to  open  our  discussion  of  them  by  giving  data  that  will 
show,  beyond  question,  the  great  need  of  improvement 
in  their  construction  and  use.  Statistics  of  scaffold 
accidents  are  hard  to  obtain,  however,  and  the  figures 
that  are  available  are  exceedingly  meager.  The 
United  States  Census  Bureau,  at  Washington,  can 
furnish  no  data  on  the  subject,  nor  can  the  various 
individual  states  of  the  Union,  except  in  a  few  cases. 
This  is  not  because  the  accidents  are  rare,  but  because 
they  are  either  not  reported  to  the  authorities,  or  not 
classified  so  that  they  can  be  abstracted  readily. 
Inquiries  that  we  have  made  in  all  the  cities  of  the 
United  States  having  a  population  of  100,000  or  more, 
show  that  few  of  them  can  furnish  data  respecting  the 
number  of  deaths  from  scaffold  accidents,  without  a 
laborious  and  impracticable  search  through  coroners' 
records.  A  number  of  these  cities  classify  their  deaths 
by  the  Bertillon  or  International  method,  which  is 
entirely  sufficient  for  most  purposes ;  but  while  scaffold 
accidents  are  occasionally  recorded  specifically  under 
this  system,  they  usually  have  no  definite  place  in  it, 


12  REALITY  OF  THE  SCAFFOLD  HAZARD 

but  are  distributed  under  such  general  heads  as 
"Fractures",  "Falls",  "Accidental  Traumatisms",  and 
the  like. 

This  being  the  situation  with  regard  to  fatal 
accidents,  it  is  not  surprising  to  find  that  the  available 
statistics  of  non-fatal  ones  are  mostly  so  incomplete 
and  fragmentary  that  to  print  any  of  them  would  be 
actually  misleading.  The  accidents  that  occur  in 
factories,  foundries,  mines,  and  other  such  localized 
centers  of  industrial  activity,  are  often  recorded  quite 
fully  by  the  State  authorities,  but  those  that  occur  in 
connection  with  construction  work  are  seldom  noted 
in  the  same  systematic  way. 

2.  Concerning  Newspaper  Items.  Since  full  and 
authoritative  statistics  of  scaffold  accidents  cannot  be 
had,  a  few  newspaper  items,  gathered  in  1911,  are  given 
below,  in  the  hope  of  conveying  a  more  or  less  definite 
idea  of  the  general  nature  of  accidents  of  this  kind, 
and  of  the  loss  of  life  and  the  number  of  personal 
injuries  that  they  commonly  involve.  These  items 
probably  represent  but  a  small  fraction  of  the  entire 
number  of  scaffold  accidents  that  occurred  during  the 
period  covered,  and  it  would  therefore  be  unjustifiable 
to  draw  any  definite  conclusions  from  them,  with  re- 
spect to  the  total  number  of  similar  accidents  that  occur 
in  the  United  States  in  one  year,  or  in  any  other  stated 
interval  of  time. 

It  should  be  understood  that  we  do  not  guarantee 
the  literal  accuracy  of  all  these  accounts,  because  we 
have  no  knowledge  of  the  facts  (save  in  a  few  cases), 
except  as  they  are  given  in  the  clippings  themselves. 
We  print  the  accounts  in  good  faith,  however,  and  we 
believe  them  to  be  correct  in  all  essential  particulars. 


LIST  OF  SCAFFOLD  ACCIDENTS 


13 


3.     Illustrative   List   of  Scaffold   Accidents. 

1 .  June  6th.     Part  of  the  scaffold  surrounding  the 
new  theater  at  Paxtang  Park,   Harrisburg,  Pennsyl- 
vania, collapsed.     One  man  fell  39  feet.     His  right  leg 
and  ankle  were  broken. 

2.  June  8th.     A  man  fell  from  a  scaffold  used  in 
the  construction  of  a  building  on   Bruce   and   Inness 
avenues,  Cincinnati,  Ohio.     He  was  badly  injured. 

3.  June  9th.     A  scaffold  broke  at  the  plant  of  the 
Astoria  Heat,    Light   &   Power  Company,    at  Casino 
Beach,  near  Astoria,  New  York.    Two  men  were  injured. 

4.  June   9th.     A  scaffold  fell    at  a  building  on 


FIG.  1.     SAFETY  SCAFFOLDING. 

(From  a  full-sized  model,  exhibited  at  the  Leipzig  Exposition  of  1913.     Fig.  2  shows  the 
same  building,  as  seen  from  the  opposite  side.) 


14  REALITY  OF  THE  SCAFFOLD  HAZARD 

East  Jackson  Boulevard  and  South  Michigan  avenue, 
Chicago.  A  man  who  was  working  upon  it  was 
thrown  to  the  pavement  and  badly  injured. 

5.  June  9th.     Three    men    fell    from  a  scaffold 
at  214  Lake  avenue,  Rochester,  New  York.     All  three 
were  more  or  less  injured. 

6.  June    9th.     A   scaffold    rope    broke    at    the 
Meise  store,  Vincennes,  Indiana.     One  man,  a  painter, 
was  killed. 

7.  June    10th.     A  man   was   injured   by  falling 
28  feet  from  a  scaffold  at  the  new  power  house  at 
Mt.  Tabor,  near  Newark,  New  Jersey. 

8.  June    12th.     A    scaffold    rope    broke    on    a 
swinging  scaffold  at  the  new  building  at  28  West  23d 
street,    New  York.     Four  iron-workers  were   on   the 
platform  of  the  scaffold  and  they  were  all  striving  to 
bring  a  huge  steel  beam  into  place.     The  rope  that 
broke   was   thereby   subjected   to   great   strain.     The 
four  men  fell  two  stories  but  none  of  them  were  danger- 
ously injured. 

9.  June    12th.     A    scaffold    collapsed    on    the 
first    floor   of    the    post-office   building,    Philadelphia, 
Pennsylvania.  A  fresco  painter  who  was  working  upon 
the  scaffold  fell  20  feet  and  was  injured. 

10.  June   12th.     A  scaffold  fell  near  Milverton, 
Ontario.     Three  men  were  seriously  injured. 

11.  June  14th.     Two  men    fell   from  a   scaffold 
at    the    Metropolitan    Museum    of    Art,    New    York 
City.     One  was  killed   and  the   other  was   seriously 
injured. 

72.  June  15th.  A  carpenter  fell  from  a  scaffold 
at  the  Good  Samaritan  Hospital  at  Clifton,  near  Cin- 
cinnati, Ohio.  He  died  two  weeks  later. 


LIST  OF  SCAFFOLD  ACCIDENTS  15 

73.  June  16th.  A  rope  broke  on  a  scaffold 
inside  the  rotunda  of  the  People's  Gas  Light  and  Coke 
Building,  Chicago,  Illinois.  One  man  was  killed  and 
another  fatally  injured.  The  men  were  engaged  in 
washing  the  walls  of  the  rotunda. 

14.  June  16th.  A  scaffold  fell  near  New  York 
City.  Two  men  were  injured. 

75.  June  16th.  A  scaffold  gave  way  at  the 
People's  Church,  East  Lansing,  Michigan.  One  man 
was  injured. 

16.  June  16th.  A  man  was  injured  serious- 
ly and  perhaps  fatally  by  falling  from  a  scaffold  at 
St.  Stephen's  Catholic  church,  Geneva,  New  York.  He 
stepped  on  the  end  of  a  plank,  which  tipped  up  under 
his  weight  and  caused  him  to  fall  30  feet. 

77.  June  16th.  An  extension  ladder  which 
was  being  used  as  a  scaffold  at  the  Grice  Building, 
Norfolk,  Virginia,  broke  short  off.  A  painter  who 
was  standing  upon  it  was  thrown  to  the  pavement 
below  and  received  injuries  from  which  he  died. 

18.  June  17th.  A  scaffold  gave  way  at  the 
Atlantic  Coast  Line  station,  Fayetteville,  North  Caro- 
lina. It  was  used  in  repairing  the  roof  of  the  building. 
Two  slaters  fell  a  distance  of  25  feet  and  were  injured. 

IQ.  June  17th.  A  man  fell  from  a  scaffold 
built  around  an  oil  tank  at  Claymont,  near  Wilmington, 
Delaware.  He  was  seriously  injured. 

20.  June    17th.     A    carpenter    was    injured    by 
falling  from  a  scaffold  at  Twin  Oaks,  near  Chester, 
Pennsylvania.     He  stepped  on  a  loose  board  and  was 
thrown  to  the  ground. 

21.  June  19th.     A  scaffold  gave  way  at  Daven- 
port, near  Marshalltown,  Iowa.     Two  men  were  injured. 


16  REALITY  OF  THE  SCAFFOLD  HAZARD 

22.  June    19th.     A  scaffold  collapsed  at   Elliott 
avenue    and    Murray    street,    Yonkers,    New    York. 
Four  men  were  injured,  and  it  was  believed  that  two  of 
them  could  not  recover. 

23.  June    21st.     A    man    was    seriously  injured 
by  falling  from  a  scaffold  on  Johnstone  avenue,  Cohoes, 
New  York. 

24.  June   21st.     Two   men  were   badly    injured 
by  falling  from  a  scaffold  on  Midvale  avenue,  Roxboro, 
Philadelphia,  Pennsylvania. 

25.  June  23d.     A   scaffold   collapsed    at   Utica, 
New'  York,    and    two  men   were   injured    by   falling 
to  the  ground. 

26.  June    24th.     A    carpenter    was    injured    by 
falling  from  a  scaffold  at  Baltimore,  Maryland. 

27.  June  26th.     A   man   was   seriously    injured 
by  falling  from  a  scaffold  on  Woodward  street,  Jersey 
City,  New  Jersey. 

28.  June  27th.     A  scaffold  collapsed  at  Yonkers, 
New    York.     Two   carpenters    were    thrown     to    the 
ground  and  injured, — one  of  them  fatally. 

2p.  June  27th.  A  scaffold  gave  way  at  Detroit, 
Michigan.  Three  men  were  thrown  to  the  ground 
and  injured. 

30.  June  27th.  A  scaffold  collapsed  in  Dry 
Dock  No.  4,  at  the  Navy  Yard,  Brooklyn,  New  York. 
One  man  was  badly  injured. 

37.  June  27th.  A  scaffold  gave  way  at  Leba- 
non, near  Albany,  New  York.  One  man  was  seri- 
ously injured. 

32.  June  30th.  The  ropes  supporting  a  swing- 
ing scaffold  gave  way  at  the  State  School  for  the  Deaf 
and  Blind,  Ogden,  Utah.  Two  painters  who  were 


LIST  OF  SCAFFOLD  ACCIDENTS 


17 


at  work  upon  it  were  thrown  fifty  feet  to  the  ground. 
One  of  them  was  killed  instantly,  and  the  other  was 
injured  seriously  and  perhaps  fatally. 

jj.  June  30th.  A  scaffold  gave  way  on  Eliza- 
beth street,  Utica,  New  York.  Two  men  were  injured. 

34.  July  1st.  A  scaffold  collapsed  in  a  sewer 
at  Sioux  City,  Iowa.  One  man  was  injured.  It 
is  reported  that  the  material  used  in  the  scaffold 
was  imperfect. 


FIG.  2.     SAFETY  SCAFFOLDING. 

(From  a  full-sized  model,  exhibited  at  the  Leipzig  Exposition  of  1913.) 
(Compare  Fig.  1.) 


18  REALITY  OF  THE  SCAFFOLD  HAZARD 

35-  July  1st.  A  scaffold  gave  way  at  the  annex 
to  the  Novelty  Works,  Duncannon,  Pennsylvania. 
One  man  was  injured. 

36.  July    3d.     A    painter    was   killed  by  falling 
from  a  scaffold  at  the  Richards  Hotel,  McKeesport, 
Pennsylvania. 

37.  July    3d.     A    man    was    killed    by    falling 
from  a  scaffold  at  Washington  and  Barrow  streets,  New 
York.     The  scaffold  was  suspended  by  ropes,  and  the 
man  who  was  injured  pushed  it  away  from  the  wall 
and  fell  through  the  opening  so  made. 

38.  July  5th.     A  scaffold  gave  way  at  Fifteenth 
street  and  Madison  avenue,  Cincinnati,  Ohio.     A  car- 
penter who  was  working  upon  it  was  injured. 

jp.  July  5th.  Two  men  were  injured  by  the 
fall  of  a  scaffold  at  the  New  Dort  School,  Flint, 
Michigan.  The  accident  was  due  to  the  breaking 
of  the  ropes  by  which  the  scaffold  was  supported.  It 
is  said  that  they  had  become  rotted  by  the  action  of 
acid  used  by  painters  in  their  work. 

40.  July    6th.     A    scaffold    fell    on    Vanderbilt 
street,  Brooklyn,  New  York.     Two  men  were  injured. 

41.  July    7th.     A   painter    fell    from    a    swing- 
ing scaffold  at  Newark,   New  Jersey,  and  was  badly 
injured. 

42.  July    7th.     A    scaffold    collapsed    at     East 
129th  street  and  Bart  field   avenue,   Cleveland,    Ohio. 
One  man  was  severely  injured. 

43-  July  7th.  A  man  was  killed  by  falling  from 
a  scaffold  at  Coffeyville,  Kansas. 

44.  July  7th.  A  painter  was  fatally  injured  by 
falling  from  a  scaffold  at  415  North  Seventh  street, 
St.  Louis,  Missouri. 


LIST  OF  SCAFFOLD  ACCIDENTS  19 

45-  July  8th.  A  man  was  seriously  injured, 
at  McKeesport,  Pennsylvania,  by  the  fall  of  a  scaffold 
that  was  used  in  tearing  down  a  building. 

46.  July  llth.     A  scaffold  fell  at  the  New  York 
Military  Academy,  Cornwall,   New   York.     One   man 
was  seriously  injured. 

47.  July  llth.     Five  men  were  injured  at  Engle- 
wood,  New  Jersey,  by  the  breaking  of  one  of  the  sup- 
ports of  a  scaffold  at  the  new  Church  of  St.  Cecilia. 

48.  July  llth.     A  carpenter  was   overcome   by 
heat  while  working  on  a  scaffold  at  Kalamazoo,  Michi- 
gan.    He  fell  to  the  ground  and  was  fatally  injured. 

49 .  July  llth.     A  man  was  fatally  injured  by 
falling  from  a  scaffold  at  Galesburg,  Michigan. 

50.  July   12th.     A  man  was  seriously  injured  by 
falling  from  a   scaffold   at   Dunstable,    near   Nashua, 
New  Hampshire. 

51.  July   13th.     A  man  was  fatally  injured  by 
falling  from  a  scaffold  at  the  new  High   School,   at 
Redford,  Indiana. 

52.  July    13th.     A    scaffold    collapsed  at  No.    2 
Elevator,  Montreal,  Quebec.     Seven  men  were  injured. 

53.  July    18th.     A   scaffold    fell    at    Gary,    In- 
diana.    One  man  was   killed   and   three   others   were 
injured. 

54.  July    18th.     A    man   was   seriously   injured 
by  falling  from  a  scaffold  in   West   Broadway,    New 
York  City. 

55.  July  18th.     A  carpenter  was  fatally  injured 
by    falling    from    a    scaffold    at    Vancouver,    British 
Columbia. 

56.  July    19th.     A   man   was  injured  by  falling 
from  a  scaffold  at  Cincinnati,  Ohio. 


20  REALITY  OF  THE  SCAFFOLD  HAZARD 

57.  July  20th.  A  scaffold  collapsed  at  Raleigh, 
near  Hamilton,  Canada.  Two  men  were  critically 
injured. 

5#.  July  20th.  A  scaffold,  used  in  repairing 
a  building,  collapsed  at  Covington,  Kentucky.  One 
man  was  injured. 

5p.  July  21st.  A  rope  broke  on  a  hanging  scaf- 
fold at  210  Washington  street,  Hoboken,  New  Jersey. 
The  scaffold  fell,  killing  one  man  and  injuring  two  others. 

60.  July    21st.     A    swinging    scaffold    used    for 
painting  the  Arcade  Building,  Toledo,  Ohio,  tipped  and 
threw  a  painter  to  the  ground.     He  was  badly  injured. 

61.  July  24th.     A  painter  was  seriously  injured 
at  Glove rsville,  New  York,  by  the  fall  of  a  scaffold. 
Some  of  the  wooden  parts  of  the  rigging  broke,  and 
the  entire  structure  crashed  to  the  ground. 

62.  July    25th.     A    man    fell    from    a    scaffold 
at  the  Caldwell  Lawn  Mower  Works,  Newburgh,  New 
York.     He  was  critically  injured. 

63.  July   25th.     A   scaffold    fell    in    the    yards 
of   the    New   York   Central   railroad,    near   Syracuse, 
New  York.     One  man  was  injured. 

64.  July  26th.     A  scaffold  gave  way  on  Maple 
street,    Jersey    City,    New   Jersey.     A  carpenter   was 
badly  injured. 

65.  July   27th.     A   painter  was   killed   by   fall- 
ing from  a  scaffold  on  Lafayette   avenue,   Brooklyn, 
New  York. 

66.  July  27th.     A  carpenter  was   badly  injured 
by  falling  from  a  scaffold  at  Cleveland,  Ohio. 

67 ' .  July  27th.  A  painter  was  seriously  injured 
by  falling  from  a  suspended  scaffold  in  the  South 
Bergen  district  of  Jersey  City  Heights,  New  Jersey. 


LIST  OF  SCAFFOLD  ACCIDENTS  21 

68.  July  27th.     A  man  was  fatally  injured  by 
falling  from  a  scaffold  at  Rochester,  New  York. 

69.  July  27th.     A  carpenter  was  fatally  injured 
by  falling  from  a  scaffold  at  the  Baptist  Church,  Nicho- 
lasville,  Kentucky. 

70.  July  31st.     Three  men  were  injured  by  the 
fall   of   a  scaffold  at  Philadelphia,    Pennsylvania.     A 
considerable  amount  of  brick   and   mortar  fell  upon 
the  scaffold  and  wrecked  it. 

77.     July  31st.     A  painter  was  killed  by  falling 
from  a  scaffold  in  Brooklyn,  New  York. 

72.  July  31st.     A  scaffold  fell  on  Park  avenue, 
Indianapolis,  Indiana.     A  tinner  was   thrown   to  the 
ground  and  seriously  injured. 

73.  July  31st.     A  carpenter  was  severely  injured 
by  the  fall  of  a   scaffold  at  the  foot  of  South  street, 
Milwaukee,  Wisconsin. 

74.  July  31st.     Two  painters  were  seriously  in- 
jured, at  Sparta,  Wisconsin,   by    the    breaking    of    a 
tackle  scaffolding. 

75.  August    1st.      Two    men    were    injured    at 
524  Cortland  street,  West  Hoboken,   New  Jersey,  by 
the  falling  of  a  scaffold  used  in  shingling  a  roof.     The 
accident  was  said  to  be  due  to  the  loosening  of  one  of  the 
brackets. 

76.  August  2d.     A  painter  was  severely  injured 
by  falling  from  a  scaffold  in  Jersey  City  Heights,  New 
Jersey.     He    inadvertently    stepped    off  the    scaffold 
backward. 

77.  August  2d.     A  painter  was  killed  by  falling 
from  a  scaffold  at  the  Albany  Hotel,  Denver,  Colorado. 

78.  August  4th.     A  man  was  painting  the  smoke- 
stack   of    the    Stearns    Automobile    Company,    when 


22  REALITY  OF  THE  SCAFFOLD  HAZARD 

a  knot  slipped  in  one  of  the  ropes  which  supported 
the  scaffold  on  which  he  was  working.  The  scaffold 
fell  and  the  man  was  seriously  injured. 

7p.     August    5th.     A   man   was  killed  by  falling 
from  a  scaffold  at  Cincinnati,  Ohio. 

80.  August  7th.     A  man  was  fatally  injured  by 
falling  from  a  scaffold  at  Rochester,  New  York. 

81.  August  9th.     A  scaffold  gave  way  at  Hous- 
ton, Texas.     A  carpenter  was  seriously  injured. 

82.  August  10th.     A  man  was  seriously  injured 
by  falling  from  a    scaffold  on   Front  avenue,    Cleve- 
land, Ohio. 

83.  August    12th.     A   scaffold  gave  way  at  the 
Co-operative  Foundry  in   Lincoln's  Park,    Rochester, 
New  York.     One  man  was  fatally  injured. 

84.  August    14th.     A   man   was  fatally   injured 
by  falling  from  a  scaffold  at  Second  and  Church  streets, 
Philadelphia,  Pennsylvania. 

85.  August    15th.     A  scaffold  gave  way  on  the 
roof  of  the  Reformed  Church,  Ellwood,  Pennsylvania. 
Two  tinners  slid   to  the  edge  of  the   roof   and  then 
plunged  to  the  ground.     One  of  them  was  killed  and 
the  other  injured. 

86.  August  17th.     A  carpenter  was  seriously  in- 
jured by  falling  from  a  scaffold  at  Rochester,  New  York. 

87.  August    17th.     A    scaffold  fell  at  a  Jewish 
church  in  course  of  construction  in  Chicago,  Illinois. 
Three  men  were  injured,  one  of  them  fatally. 

88.  August  1 7th.     A  scaffold  gave  way  on  Augus- 
tine street,  Rochester,  New  York.     Two  men  were  in- 
jured, one  of  them  fatally. 

8p.     August  18th.     Two  men  were   seriously  in- 
jured by  falling  from  a  scaffold  under  the  skylight  of 


LIST  OF  SCAFFOLD  ACCIDENTS 


23 


the  Sackett  School,  Cleveland,  Ohio.  A  plank  broke 
while  the  men  were  standing  on  it. 

go.  August  18th.  A  scaffold  fell  in  the  new 
Lakewood  Theater,  Cleveland,  Ohio.  Four  men  were 
injured. 

gi.     August    23d.     Two    masons   were    seriously 


FIG.  3.     MISCELLANEOUS  SCAFFOLDS:     GERMAN  PRACTICE. 

(From  a  model,  constructed  about  one-tenth  actual  size.      Other  views  of  this  model  are 
given  in  Figs.  4  and  7.) 


24  REALITY  OF  THE  SCAFFOLD  HAZARD 

hurt  by  the  fall  of  a  scaffold  at  the  new  Sunday 
School  Building,  on  East  Dauphin  street,  Philadelphia, 
Pennsylvania.  The  accident  was  apparently  due  to 
the  overloading  of  the  platform  of  the  scaffold  with 
blocks  of  granite. 

92.  August  24th.  A  painter  was  injured  by  fall- 
ing from  a  scaffold  on  Canal  street,  Lyons,  New  York. 

4.  Comments  on  the  Foregoing  List.  It  will  be 
noted  that  in  something  like  forty  per  cent,  of  the  acci- 
dents reported  above,  men  fell  from  the  scaffold  while 
the  structure  itself  remained  undisturbed  so  far  as  can 
be  judged  from  the  information  that  is  given.  It  is 
probable  that  in  the  majority  of  these  cases  the  accidents 
would  not  have  occurred  if  suitable  hand-rails  and 
other  protective  devices  had  been  provided  and  the 
platform  planks  or  boards  had  been  properly  laid.  It 
is  fair,  therefore,  to  count  these  many  preventable 
cases  of  simple  falls  as  accidents  due  to  defects  in  the 
scaffolds, — because  an  error  in  design  is  a  defect,  just 
as  surely  as  is  a  flaw  in  the  actual  physical  material. 

It  is  worthy  of  remark  that  the  foregoing  list, 
which  is  based  upon  newspaper  items  covering  the 
92  days  of  June,  July,  and  August,  happens  to  contain 
accounts  of  exactly  92  scaffold  accidents, — which 
corresponds  to  an  average  of  precisely  one  accident 
per  day.  Moreover,  these  92  accidents  resulted  in  the 
deaths  of  3 1  persons,  and  in  more  or  less  serious  injuries 
to  115  others.  The  experience  and  observation  of 
THE  TRAVELERS  INSURANCE  COMPANY,  extending  over 
many  years,  indicates  that  the  scaffold  accidents  by 
which  men  are  killed  or  injured  in  the  United  States 
would  be  found  to  far  exceed  one  a  day,  if  they  could 
all  be  included;  and  in  view  of  this  fact,  and  of  the 


COMMENTS  ON  THE  FOREGOING  LIST  25 

further  fact,  already  noted,  that  scaffolding  has  practi- 
cally no  literature  at  the  present  time,  it  was  thought 
best  to  devote  one  entire  volume  of  THE  TRAVELERS' 
series  to  it,  as  a  contribution  toward  the  establishment 
of  a  standard  approved  practice,  in  the  interest  of 
increased  safety. 


II.     SCAFFOLDS  CONSIDERED  GENERALLY. 

5.  Forms  and  Uses  of  Scaffolds.     Scaffolds  and 
stagings  are  built  in  many  different  forms,  according 
to  the  purposes  they  are  to  serve.     They  are  used  in  new 
building  construction,  in  repair  work  on  old  buildings, 
in  riveting,   in  building  chimneys,  in  pointing  brick- 
work, in  cleaning  walls,  in  plastering,  painting,  paper 
hanging  and  decorating,  and  in  various  other  opera- 
tions which  need  not  be  enumerated.     In  some  of  these 
applications  (as,  for  example,  in  plastering  or  painting 
rooms  of  ordinary  height)  the  workmen  are  elevated 
only  four  or  five  feet.     A  fall  from  this  height  often 
results  in  painful  injuries  but  it  rarely  results  in  death, 
and  in  the  majority  of  cases  the  men  escape  entirely 
without  harm.     In  many  other  cases,   however,   the 
men  have  to  work  at  a  considerable  height  above  the 
ground,  or  above  the  nearest  floor  to  which  they  might 
fall  in  the  event  of  an  accident;  and  we  shall  give  the 
major  part  of  our  attention  to  the  forms  of  scaffold 
that  are  used  for  work  of  this  more  hazardous  nature, 
where  a  fall  is  almost  certain  to  be  accompanied  either 
by  death  or  by  personal  injuries  of  the  most  serious 
nature. 

6.  Scaffolds    for    Building.     These    include    the 
forms  used  by  bricklayers,   masons,   carpenters,   and 
certain  other  classes  of  artisans.     The  types  that  are 
used  chiefly  by  bricklayers  and  masons  will  receive 
particularly  full  treatment,  because  nearly  all  of  our 
modern  high  buildings  are  built  of  brick  or  stone,  or 


POLE  SCAFFOLDS  27 

(more  recently)  of  concrete,  and  carpenters'  stagings 
are  employed  mainly  upon  lower  buildings  and  for 
auxiliary  operations  such  as  roofing  and  inside  finishing. 

The  scaffolds  that  are  used  in. building  operations 
by  bricklayers  and  masons  may  be  divided  into  three 
main  classes,  which  may  be  designated,  according  to 
their  respective  natures,  as  "pole  scaffolds",  "suspended 
scaffolds",  and  "outrigger  scaffolds". 

7.  Pole  Scaffolds.  Of  the  three  main  types  just 
enumerated,  the  "pole  scaffold"  is  by  far  the  common- 
est. It  is  so  named  because  its  weight  is  supported, 
either  wholly  or  in  part,  by  poles  or  uprights  that  rest 
upon  the  ground,  or  upon  a  sill  or  some  other  foundation 
that  itself  rests  upon  the  ground.  Scaffolds  of  this 
type  are  also  called  "fixed  scaffolds",  from  the  fact 
that  they  remain  in  place  until  the  wall  that  is  to  be 
erected  is  completed;  but  the  name  "pole  scaffold"  is 
preferable,  because  it  is  more  precise  and  descriptive. 
Pole  scaffolds  are  not  adjustable  in  any  way,  and  they 
are  changed,  as  the  work  proceeds,  only  by  building 
on  to  them  above,  so  as  to  extend  them  upward,  or 
by  shifting  the  platforms  upon  which  the  men  work,  by 
removing  the  planking  from  one  level  and  relaying  it 
anew  at  a  higher  one.  The  most  essential  characteristic 
of  the  pole  scaffold  is  that  its  weight  is  supported  by  a 
thrust  or  pressure  upon  the  poles  or  upon  the  wall  that 
is  being  built,  and  never  by  a  tension  upon  cables  or 
other  similar  or  equivalent  devices. 

The  pole  scaffold  is  fairly  uniform  in  design 
throughout  the  United  States,  and  the  forms  that  are 
used  here  differ  chiefly  in  matters  of  detail  from  those 
that  are  employed  in  Europe  for  similar  purposes.  In 
this  country,  for  example,  the  parts  of  the  scaffold  are 


28 


SCAFFOLDS  CONSIDERED  GENERALLY 


fastened  to  one  another  mainly  by  nailing,  and  they 
are  made  of  sawed  lumber  almost  exclusively;  but  in 
England  and  in  continental  Europe  the  parts  are  held 
together  largely  by  clamps  or  ropes,  and  a  considerable 
use  is  made  of  round  wood,  this  consisting  of  the  original 


FIG.  4.     MISCELLANEOUS  SCAFFOLDS:     GERMAN  PRACTICE. 

(From  a  model,  constructed  about  one-tenth  actual  size.     Compare  Figs.  3  and  7.) 


POLE  SCAFFOLDS  29 

sticks,  perhaps  shaved  down  a  little,  but  substantially 
of  the  size  to  which  they  grew,  and  with  their  fibers 
practically  uncut. 

Scaffolds  that  are  used  for  laying  stone, should  be 
more  strongly  built  than  those  used  for  laying  brick, 
because  they  are  likely  to  be  loaded  more  heavily. 
The  difference  in  the  loading  is  less  marked  in  the 
United  States  than  it  is  in  some  foreign  countries, 
because  here  the  stone  that  is  to  be  laid  is  usually 
delivered  ready  for  immediate  use,  whereas  in  England, 
for  example,  it  is  often  deposited  upon  the  scaffold 
while  there  is  still  a  considerable  amount  of  work  to  be 
done  to  it  in  the  way  of  trimming  or  fitting  or  other 
preparation.  In  American  practice  the  stone  is  com- 
monly hoisted  directly  to  its  final  position,  without 
having  its  weight  thrown  upon  the  scaffold  at  all;  and 
in  fact  the  scaffold  upon  which  the  stone  masons  stand 
is  usually  inside  of  the  wall  that  is  going  up,  while  the 
stone  is  hoisted  on  the  outside.  Yet  scaffolds  for  laying 
stone  are  also  used  more  or  less,  in  the  United  States, 
in  such  a  way  that  there  is  likelihood  of  their  serving 
to  some  extent  as  temporary  storage  places  for  some 
of  the  stone;  and  in  every  case  of  this  kind  special 
care  should  be  taken  to  have  all  of  the  parts  of  the 
scaffold  particularly  stout  and  strong.  (See  paragraph 
57,  page  90.) 

The  independent  pole  scaffold  is  distinguished  from 
what  is  known  as  the  bricklayers'  pole  scaffold  not 
only  by  its  greater  strength,  but  also  by  one  conspicu- 
ous and  noteworthy  structural  detail.  In  laying  a 
brick  wall  by  the  aid  of  a  pole  scaffold  it  is  usual  to 
utilize  the  wall  itself  for  supporting  the  inner  edge 
of  the  working  platform,  so  that  in  this  type  there  is 


30 


SCAFFOLDS  CONSIDERED  GENERALLY 


FIG.  5.     SKELETON  OF  A  BRICKLAYERS'  POLE  SCAFFOLD. 

(Platform,  braces,  guard-rails,  and  foot-boards  omitted.) 


FIG.  6.     SKELETON  OF  AN  INDEPENDENT  POLE  SCAFFOLD, 

(Platform,  braces,  guard-rails,  and  foot-boards  omitted.) 


SUSPENDED  SCAFFOLDS  31 

but  one  row  of  uprights.  On  the  other  hand,  in  build- 
ing with  stone  it  is  not  customary  to  depend  upon  the 
wall  for  sustaining  any  part  of  the  weight  of  the  scaf- 
fold, the  support  afforded  by  the  wall  when  building 
with  brick  being  obtained  by  providing  a  second 
row  of  poles,  set  close  to  the  stonework. 

The  scaffold  with  two  rows  of  poles  is  self-sus- 
taining (in  the  sense  that  it  is  independent  of  the  wall) , 
and  for  that  reason  we  shall  call  it  the  "independent" 
scaffold  throughout  the  present  work. 

It  should  not  be  understood  that  the  bricklayers' 
scaffold  is  used  solely  for  laying  brick,  nor  that  the 
independent  scaffold  is  used  solely  for  laying  stone.  It 
is  convenient  to  retain  the  names  that  custom  has  at- 
tached to  them,  so  that  either  type  of  scaffold  may  be 
quickly  and  simply  designated;  but  the  independent 
type  with  its  two  rows  of  supporting  poles  can  be  ap- 
plied equally  well  to  the  building  of  brick  walls,  and  an 
unmistakable  and  increasing  tendency  to  use  it  in  this 
way  has  in  fact  been  noticeable  in  the  last  few  years.  It 
is  also  commonly  adopted  in  repair  work  and  for  other 
purposes,  in  connection  with  walls  that  are  already 
built  and  which  have  no  openings,  or  an  insufficient 
number  of  conveniently -situated  openings,  for  receiving 
the  ends  of  the  cross-beams  or  putlogs  that  support 
the  platform  in  the  bricklayers'  type. 

8.  Suspended  Scaffolds.  The  pole  scaffolds,  just 
considered,  are  used  quite  widely  in  the  erection  of 
buildings  that  are  not  more  than  five  stories  high  or 
thereabouts,  and  upon  higher  ones  when  they  have  no 
framework  of  structural  steel.  Modern  builders  greatly 
favor  the  steel  framework  for  buildings  of  more  than 
five  stories  or  so,  however,  and  when  it  is  adopted  some 


32  SCAFFOLDS  CONSIDERED  GENERALLY 

form  of  swinging  scaffold  can  be  used  by  the  bricklayers 
with  advantage.  In  putting  up  a  steel-framed  building 
with  the  aid  of  such  a  scaffold  the  steelwork  is  carried 
up  to  a  considerable  distance  before  the  laying  of  brick 
begins,  and  when  the  frame  has  reached  a  suitable 
height  the  scaffold  is  installed.  It  consists  essentially 
of  a  platform  swung  from  the  upper  part  of  the  steel 
framework  by  means  of  steel  cables,  or  steel  straps, 
and  so  designed  and  arranged  that  the  level  of  the 
platform  can  be  conveniently  raised  as  the  \vork  pro- 
gresses. When  cables  are  used,  the  platform  is  usually 
shifted  by  means  of  windlasses  that  wind  up  the  cables, 
and  when  the  support  is  afforded  by  steel  straps  these 
are  perforated  at  intervals,  so  that  the  cross-beams  or 
putlogs  supporting  the  platform  can  be  raised  from 
time  to  time,  and  shifted  to  new  positions. 

The  mechanism  by  which  the  platform  is  shifted 
varies  somewhat  in  the  different  makes  of  scaffold,  and 
in  a  later  division  of  this  work  two  or  three  of  the 
standard  forms  of  it  are  described  in  some  detail. 
The  types  of  scaffold  in  which  the  platform  is  supported 
by  flexible  cables  are  far  more  commonly  met  with,  at 
the  present  day,  than  those  in  which  steel  straps  are 
employed. 

Advocates  of  the  swinging  scaffold  assert  that  it 
is  far  safer  than  the  pole  type  for  use  on  high  buildings, 
and  this  claim  is  undoubtedly  justifiable  when  the 
scaffold  is  in  good  condition  and  is  properly  installed 
and  handled.  A  pole  scaffold  is  practically  out  of  the 
question,  in  fact,  for  use  on  an  American  "sky-scraper," 
because  it  would  have  to  be  exceedingly  substantial 
and  massive  to  be  safe  against  collapse  from  its  own 
weight  and  its  load  of  materials  and  the  side  stresses 


OUTRIGGER  SCAFFOLDS  33 

due  to  the  wind  and  other  causes,  and  its  cost  would 
also  be  prohibitive. 

9.  Outrigger  Scaffolds.     In  the  "outrigger"  scaf- 
fold the  platform  is  supported  upon  beams  or  outriggers 
(which  are  also  known  as  "cantilevers",  or  "thrust- 
outs",  and  by  various  other  names),  which  extend  out 
through  windows  or  other  openings  in  the  walls,  and 
which  are  secured  solidly  to  the  framework  or  flooring, 
inside  of  the  building.     Outriggers  are  used  also  in 
connection  with  suspended  scaffolds,  but  the  distinction 
between   the   suspended  scaffold   and  the    "outrigger 
type"  consists  in  the  fact  that  in  the  suspended  scaf- 
fold the  platform  is  hung  from  the  outriggers,  while 
in  the   outrigger  type  the  platform   rests   upon   the 
outriggers  either  directly  or  by  the  mediation  of  some 
simple  structure  designed  to  raise  the  platform  to  a 
somewhat  more  convenient  height. 

In  building  operations  outrigger  scaffolds  are  used 
somewhat  (though  fortunately,  as  we  believe,  to  a 
diminishing  extent)  for  the  support  of  one  or  more 
layers  of  horses,  upon  which  planks  are  laid  for  sus- 
taining the  workmen.  Outrigger  scaffolds,  when  used, 
must  be  carefully  designed  and  secured,  and  it  is  pre- 
ferable to  make  use  of  some  other  form  when  this  can 
be  done  without  prohibitive  expense  or  difficulty. 

10.  Construction  Practice  in  General.     In  England 
a  scaffold  is  usually  built  only  on  one  side  of  a  brick 
wall,  if  the  wall  is  9  inches  thick,  but  for  all  brick  walls 
of  a  greater  thickness,  and  for  walls  built  of  stone,  it  is 
usual  to  erect  a  scaffold  on  both  sides.     In  the  United 
States  the  practice  is  so  varied  that  no  general  statement 
of  this  sort  can  be  made.     In  some  parts  of  the  country 
the  bricklaying,  when  the  building  is  not  too  large, 


34  SCAFFOLDS  CONSIDERED  GENERALLY 

is  done  mainly  or  altogether  from  the  inside.  This 
is  called  "overhand  laying"  and  it  has  the  advantage 
that  no  scaffold  is  required,  the  work  of  the  bricklayers 
being  done  from  horses  that  stand  upon  the  floors, 
inside, — the  floors  being  laid  as  the  walls  go  up.  The 
overhand  method,  on  the  other  hand,  is  regarded  with 
disfavor  by  many  builders,  on  the  ground  that  it  is  hard 
to  make  a  good-looking  wall  in  this  way,  because  in 
finishing  the  outside  surface  the  men  have  to  lean  over 
"soft"  courses  of  brick,  and  work  at  a  disadvantage. 

In  the  United  States  it  is  becoming  increasingly 
common  to  expedite  the  bricklaying  by  building  from 
both  sides  of  the  wall  at  once,  the  inner  courses  of  brick 
being  laid  from  the  floors  by  the  aid  of  horses,  while 
the  outer  courses  are  laid  from  the  outside  by  means  of 
a  suspended  scaffold,  hung  from  the  steel  skeleton  of 
the  building  as  already  described. 

11.  Carpenters'    Outside    Stagings.      Carpenters' 
stagings,   as  applied  in  building  wooden  houses,   are 
usually  supported  by  brackets  from  the  woodwork  of  the 
building  itself.     Those  used  for  shingling  are  sometimes 
supported  by  brackets  made  to  conform  with  the  slope  of 
the  roof,  and  sometimes  they  consist  merely  of  stringers 
laid  along  the  roof  horizontally,  and  made  fast  to  it. 

12.  Painters'   Outside   Stagings.     Painters'    stag- 
ings, when  used  for  outside  work,  commonly  consist 
of  narrow  platforms,   suspended  by  means  of   ropes 
hanging  from  hooks  secured  to  the  building  above,  or 
by   some  other  equivalent  means.     The  boatswain's 
chair,  consisting  of  a  seat  of  some  kind  suspended  by  a 
rope,  is  often  used  for  light  work. 

13.  Plasterers'    and  Decorators'  Inside  Stagings. 
In    finishing    the   interior  of   a   building,    carpenters, 


MISCELLANEOUS  SCAFFOLDS  35 

plasterers,  and  decorators  make  use  of  stagings  which, 
although  they  are  built  in  various  forms,  are  neverthe- 
less reducible  to  a  few  general  types.  One  of  the  most 
important  of  these  is  similar  in  general  nature  to  the 
independent  pole  scaffold  mentioned  above,  it  being 
supported  by  uprights  resting  upon  the  floor,  cross- 
pieces  being  secured  to  these  for  sustaining  the  plank 
platforms  upon  which  the  workers  stand. 

14.  Ladder  Scaffolds.     For  certain  kinds  of  work 
use  is  sometimes  made  of  ladder  scaffolds,  in  which. the 
platform  is  supported  from  the  rungs  of  specially -con- 
structed ladders  that  are  placed  in  vertical  or  nearly 
vertical   positions,  and   supported  in  some  safe  man- 
ner.*    Horizontally -placed  ladders  are  also  used  to  a 
considerable  extent  in  light  scaffold  work,  to  support 
the  boards  upon  which  the  men  stand. 

15.  Small   Hanging   Stagings.     For   small   work 
about  buildings,  as  in  repairing  or  in  attending  to  small 
detail  work  where  no  great  weight  is  to  be  sustained, 
it  is  common  to  throw  out  from  the  windows  of  a  build- 
ing a  hanging  staging,  which  is  supported  from  firmly 
secured  horizontal  beams  or  outriggers,  passing  out 
from  the  windows  perpendicularly  to  the  wall  of  the 
building.     These  differ  from  the  builders'  suspended 
scaffolds  described  above  in  being  of  a  far  lighter  type 
of  construction,  and  they  also  differ  from  them  widely 
in  their  structural  details. 

16.  Chimney  Stagings.     In  the  construction  of 
factory  chimneys  it  is  customary  to  build  a  staging 
circularly  around  the  chimney,  at  least  near  its  base, 
and  sometimes  to  its  entire  height.     A  second  one  is 
usually  built  inside  the  chimney  also.     These  stagings 

*Scaffolds  of  this  nature  are  extensively  employed  in  Germany,  and  a  further  description  of 
them  will  be  found  in  paragraph  69,  page  123. 


36  SCAFFOLDS  CONSIDERED  GENERALLY 

frequently  run  up  to  great  elevations,  and  they  must  be 
made  correspondingly  secure.  For  making  local  repairs 
a  hanging  staging  is  sometimes  suspended  from  the  top 
of  the  chimney,  and  swung  down  to  the  place  where  the 
work  is  to  be  done. 

17.  Other  Forms  of  Scaffolds.  Various  other 
forms  of  scaffolds,  which  we  cannot  fully  enumerate, 
are  used  in  addition  to  those  mentioned  above.  Among 
these,  for  example,  are  the  stagings  that  are  employed 
for  the  support  of  hoisting  devices  and  the  like,  these 
being  erected  either  outside  of  the  building  that 


FIG.  7.     MISCELLANEOUS  SCAFFOLDS:     GERMAN  PRACTICE. 

(From  a  model,  constructed  about  one-tenth  actual  size.     Compare  Figs.  3  and  4.) 


STRUCTURES  SIMILAR  TO  SCAFFOLDS  .     37 

is  going  up,  or  inside  ot  it, — the  object  of  such  a  staging 
being  to  elevate  the  hoisting  machine,  or  the  sheaves 
over  which  its  ropes  run,  sufficiently  to  insure  conven- 
ience and  facility  in  the  delivery  of  the  materials  to 
the  workmen.  The  latticed  towers  that  are  coming 
into  general  use  in  connection  with  concrete  work  are 
examples  of  this  type. 

18.  Structures  Similar  to  Scaffolds.  False  Work. 
There  are  many  structures  which  are  not  true  scaffolds, 
but  which  may  nevertheless  be  classed  with  them,  since 
they  involve  similar  elements  of  design,  and  are  subject 
to  somewhat  similar  dangers  in  their  operation.  Ex- 
amples of  these  are  afforded  by  the  false  centers  of 
arches,  and  by  the  supports  that  are  provided  for 
concrete  superstructures,  these  being  of  a  temporary 
nature,  and  designed  to  be  taken  down  when  the  ma- 
terial has  become  sufficiently  hard. 


HI.     THE    BRICKLAYERS'    POLE    SCAFFOLD: 
AMERICAN  PRACTICE. 

19.  General   Description.     In   the    standard    (or 
typical)  bricklayers'  scaffold,  as  built  and  used  in  the 
United  States  in  the  construction  of  brick  walls,  the 
platform  upon  which  the  workmen  stand  is  supported 
by   horizontal   cross-pieces   that    are   properly   called 
putlogs,   but  which  are  also  known,   colloquially,   as 
"putlocks"    or    "puds",    and   sometimes   as    "spuds". 
These  run  perpendicularly  to  the  wall  of  the  building, 
and  each  is  supported  at  one  end  by  the  wall  that  is 
being  erected,  a  brick  being  omitted  from  the  face  course 
for  this  purpose,  so  that  the  end  of  the  putlog  may  enter 
the  wall  and  have  a  proper  bearing. 

The  outer  ends  of  the  putlogs  rest  upon  horizontal 
stringers  called  "ledgers",  or  "running  strips",  which 
run  parallel  to  the  wall  of  the  building,  and  are  nailed 
to  uprights  or  poles  resting  solidly  upon  the  ground. 

The  bricklayers'  scaffold,  as  thus  constructed,  is 
sometimes  called  the  "Boston  scaffold".  Its  general 
characteristics  are  shown  in  Fig.  8,  and  we  proceed  to 
consider  its  various  parts  in  detail. 

THE  POLES  OR  UPRIGHTS 

20.  Material,  Quality,  and  Size.     In  England  the 
poles  or  uprights  are  usually  made  of  fir  and  are  round 
in  form,  being  about  five  inches  in  diameter  and  some 
thirty  feet  long ;  but  in  the  United  States  sawed  spruce 


MATERIAL  AND  SIZE  OF  POLES  39 

is  commonly  used  for  the  poles,  and  it  is  the  best  of  the 
woods  that  are  available  for  the  purpose.  Hemlock 
should  never  be  employed,  because  it  is  brittle,  and  is 
likely  to  break  suddenly,  under  a  heavy  load,  with  no 
warning. 

The  poles  should  be  straight,  and  they  should  also 
be  straight -grained  and  free  from  bad  knots  and  all 
other  imperfections.  Twisted  (or  "winding")  pieces 
should  not  be  used  for  poles,  because  the  ledgers  and 
braces  that  are  required  in  the  construction  of  the 
scaffold  cannot  be  nailed  to  such  poles  properly. 

In  erecting  the  poles,  care  should  be  taken  to 
have  them  as  nearly  plumb  (or  vertical)  as  possible. 
This  is  particularly  important,  because  any  serious 
departure  from  the  truly  vertical  position  imperils 
the  stability  of  the  whole  scaffold. 

For  ordinary  work,  where  the  wall  to  be  built  is 
not  more  than  four  or  five  stories  in  height  and  the 
platform  of  the  scaffold  is  not  loaded  with  more  than 
the  usual  weight,  the  uprights,  if  of  sound  spruce 
wood  as  specified  above,  may  be  as  small  as  four  inches 
square.  They  are  quite  commonly  made  of  stock 
measuring  3  in.  by  4  in.,  but  we  strongly  recommend 
the  adoption  of  four  inches  as  the  least  dimension  in 
ordinary  work. 

21.  Poles  of  Extra  Strength.  For  higher  build- 
ings, and  for  use  upon  work  where  the  platform  is  likely 
to  be  loaded  more  heavily  than  usual,  the  size  of  the 
poles  should  be  correspondingly  increased.  In  fact,  it 
is  often  well  to  make  the  poles  of  two  or  even  three 
parts,  when  the  load  is  heavy  or  the  structure  is  un- 
commonly high,  the  constituent  parts  being  placed 
side  by  side,  and  securely  bolted,  clamped,  nailed,  or 


40 


BRICKLAYERS'   POLE  SCAFFOLD 


SPACING  OF  THE  POLES  41 

lashed  together,  so  as  to  act  like  a  single  piece.  When 
two  or  more  poles  are  thus  secured  together  to  form 
one  upright,  they  should  "break  joints"; — that  is, 
the  splice  or  joint  in  any  one  of  the  constituent  poles 
should  always  come  opposite  the  continuous  portions 
of  the  other  poles  with  which  it  is  associated. 

22.  Distance  of  the  Poles  from  the  Wall.     It  is  de- 
sirable to  place  the  poles  as  near  to  the  wall  as  prac- 
ticable, because  the  cross-beams  (or  putlogs)  that  hold 
up   the   platform   should   not   be   made   longer   than 
necessary,  between  supports.     The  standard  practice 
is  to  set  the  poles  so  that  there  is  a  clear  space  of  4  ft. 
6  in.  between  them  and  the  wall.     No  greater  interval 
than  this  should  be  permitted,  unless  the  putlogs  are 
correspondingly  strengthened. 

23.  Spacing  of  the  Poles,   Parallel  to  the  Wall. 
In  the  usual  (or  standard)  construction,  the  poles  are 
spaced,  parallel  to  the  wall,  at  a  distance  of  7  ft.  6  in. 
from  center  to  center   (16  ft.  platform  planks  being 
then  used).     When,  for  any  reason,  it  is  impracticable 
to  adopt  this  uniform  interval  at  all  parts  of  the  scaf- 
fold, the  spacing  may  be  uniformly  reduced  throughout, 
or  the  width   of   one   or  more   of   the   pole-intervals 
(or  bays)  may  be  lessened,  while  the  remaining  poles 
remain  spaced  at  the  standard  distance  of  7  ft.  6  in. 
between   centers.     In   no   case,    however,    should   the 
interval  between  any  two  consecutive  poles,  as  meas- 
ured in  a  direction  parallel  to  the  wall  of  the  building, 
exceed  7  ft.  6  in.     (In  England  the  poles  are  often  set 
8  ft.  apart,  and  in  Germany  they  may  be  as  far  apart 
as  three  meters,  or  9  ft.   10  in.;  but  in  English  and 
German  practice  the  scaffold  is  designed  differently 
from  our  own  in  other  respects  also,  and  allowance  is 


42 


BRICKLAYERS'  POLE  SCAFFOLD 


made,  in  proportioning  the  parts,  for  the  increased 
stresses  that  arise  from  the  greater  intervals  between 
the  poles.) 

24.  Bearing  of  the  Pole  at  its  Lower  End.  The 
uprights  of  a  pole  scaffold  should  never  be  allowed  to 
simply  rest  upon  the  surface  of  the  ground.  They 
should  always  be  securely  fixed  at  their  lower  ends,  so 
that  a  displacement,  in  any  direction  whatsoever,  shall 
be  altogether  impossible.  Under  ordinary  conditions 


FIG.  9.     SCAFFOLD  POLE  IMPROPERLY  SECURED  AT  THE  FOOT. 

(The  builder  who  had  charge  of  the  job  on  which  this  was  found  is  a  man  of  unusual  intelli- 
gence, yet  he  considered  this  support  "good  enough".  Cases  far  worse  tnan  the  one  here 
snown  are  common.) 


SECURITY  OF  FOOT  OF  POLE  43 

a  hole  should  be  dug  in  the  ground  to  receive  the  foot 
of  each  pole,  the  hole  being  not  less  than  8  in.  or  10  in. 
deep,  and  not  larger  in  diameter  than  is  necessary  for 
the  purpose  in  view.  The  end  of  the  pole  should  be 
placed  centrally  in  the  hole,  and  be  brought  firmly 
against  the  undisturbed  earth  at  the  bottom,  if  this 
be  hard  and  stony;  after  which  the  soil  that  has  been 
removed  should  be  put  back  again,  and  be  solidly 
rammed  in  around  the  foot  of  the  pole. 

When  the  soil  is  of  such  a  soft  nature,  either  by 
reason  of  its  natural  character  or  because  of  recent 
heavy  rains,  that  there  is  reason  to  fear  that  the  pole 
might  sink  into  it,  even  slightly,  when  the  scaffold  has 
been  erected  and  put  into  service,  the  hole  that  is  dug 
to  receive  the  pole  should  be  made  larger  than  usual, 
and  a  stout  and  sound  block  or  piece  of  plank,  about 
a  foot  square  and  not  less  than  two  inches  thick,  should 
be  placed  at  the  bottom  of  the  hole  to  distribute  the 
load.  Care  should  be  taken  to  see  that  the  block  is 
approximately  level,  and  that  all  parts  of  its  under 
surface  rest  securely  against  the  earth  below.  The  pole 
should  be  solidly  fastened  to  the  center  of  the  block, 
either  by  four  or  more  large,  stout  nails,  or  by  some 
other  equally  effective  means.  The  hole  is  then  to  be 
filled  up  as  before,  and  the  filling  well  rammed  in. 

If  the  scaffold  is  to  remain  in  place  for  a  long  time, 
the  bottom  of  the  pole  should  be  well  coated  with  tar 
to  a  height  of  about  six  inches  above  the  surface  of  the 
ground.  This  precaution,  which  is  to  guard  against 
rotting,  is  of  course  unnecessary  when  the  poles  are  to 
stand  for  only  a  few  weeks. 

When  holes  cannot  well  be  dug  for  receiving  the 
poles  (as,  for  example,  when  the  poles  must  come  direct- 


44  BRICKLAYERS'  POLE  SCAFFOLD 

ly  over  a  stone  sidewalk  or  street),  some  other  equally 
effective  means  of  fixation  should  be  substituted. 
For  example,  the  poles  may  be  made  fast  to  a  stout 
sill,  which  is  itself  secured  in  some  safe  and  proper 
manner,  by  braces  or  shores  or  otherwise.  Detailed 
general  advice  respecting  the  method  to  be  used  can 
hardly  be  given,  because  much  depends  upon  the  exact 
conditions  that  must  be  met;  but  whatever  these 
conditions  are,  some  means  should  be  found  and  applied, 
for  so  fixing  the  poles  at  their  lower  ends  that  they 
cannot  become  displaced,  either  by  sinking  into  the 
ground  or  by  sliding  sidewise. 

It  was  formerly  more  or  less  common  to  place 
the  lower  end  of  the  pole  centrally  in  a  barrel  or  cask, 
which  was  then  filled  with  sand  or  earth,  solidly 
rammed  in.  This  method  is  now  seldom  used  in  the 
United  States,  but  it  is  sometimes  worth  consideration. 
While  it  is  far  inferior  to  burying  the  end  of  the  pole 
in  the  manner  described  above,  it  is  equally  superior 
to  the  common  but  improper  practice  of  merely  letting 
the  end  rest  upon  the  surface  of  the  ground,  without 
any  form  of  safeguard  or  protection. 

It  should  always  be  remembered  that  wagons  are 
likely  to  back  up  against  the  uprights,  in  the  course 
of  the  work  that  must  go  on  about  the  foot  of  a  scaf- 
fold, and  beams  or  other  materials  that  are  being 
handled  may  also  swing  against  them.  It  is  therefore 
important  to  make  the  uprights  far  more  secure  than 
they  would  need  to  be  for  the  mere  support  of  the  nor- 
mal weight  they  have  to  bear. 

25.  Landslides  or  Slips.  Care  should  be  taken, 
not  only  to  see  that  the  poles  do  not  sink  into  the 
ground,  and  that  they  are  neither  displaced  nor  broken, 


SPLICING  THE  POLES  45 

but  also  to  see  that  the  ground  upon  which  they  rest 
is  itself  solid  and  secure.  The  poles  may  have  to  be 
erected  in  the  vicinity  of  a  cesspool  or  an  old  well  or 
some  other  excavation,  or  near  the  upper  edge  of  a 
bank  or  terrace;  and  in  such  cases  it  is  important  to 
consider  the  possibility  of  the  sliding  or  slipping  of  the 
ground,  under  the  influence  of  the  extra  load  thrown 
upon  it  by  the  weight  that  will  rest  upon  the  scaffold 
poles.  Dangers  of  this  kind  vary  with  the  nature  of 
the  soil,  and  the  same  soil  is  more  hazardous  when  wet 
than  it  is  when  dry.  After  a  heavy  rain  the  ground 
about  the  foot  of  a  scaffold  should  be  carefully  con- 
sidered, in  all  cases  of  this  kind,  to  determine  whether  the 
increase  in  its  moisture  may  not  have  made  the  footings 
of  the  poles  insecure.  Danger  from  this  source  may 
often  be  overcome  by  bracing  or  shoring  the  uprights  to 
some  solid  structure  near  by ;  but  each  problem  of  this 
kind  must  be  considered  by  itself,  and  solved  with  refer- 
ence to  the  special  circumstances  under  which  it  arises. 
26.  Splicing  or  Lengthening  the  Poles.  The  poles 
or  uprights  that  are  used  in  the  construction  of  brick- 
layers' scaffolds  in  the  United  States  are  usually  from 
20  to  25  feet  in  length,  and  when  it  is  necessary  to 
carry  the  scaffold  to  a  greater  height  than  this,  they 
must  be  extended  in  some  way.  To  increase  the  height 
of  an  upright,  a  second  pole  is  erected  upon  the  end  of 
the  first  one ;  and  this  part  of  the  work  must  be  carried 
out  carefully  and  intelligently,  so  that  the  joint  or  splice 
may  be  safe  in  all  respects.  In  Europe  it  is  customary 
to  let  the  two  poles  that  are  to  be  joined  overlap  each 
other  by  five  or  six  feet,  and  to  bind  them  together 
securely  by  clamps,  rope,  or  metal  cord;  but  in  this 
country  the  upper  pole  is  set  squarely  upon  the  end  of  the 


46 


BRICKLAYERS'  POLE  SCAFFOLD 


FIG.    10.     A  SCAFFOLD   POLE,   CUT   OFF  WHILE  THE  SCAFFOLD 

WAS   IN   USE. 

(The  pole  marked  "B"  was  a  short,  auxiliary  one,  which  was  not  secured  to  the  rest  of  the 
structure  solidly  enough  to  receive  much  of  the  load.  The  one  marked  "A"  was  the  true 
corner  pole  of  the  scaffold,  and  some  person  had  sawed  it  off,  presumably  because  it  was 
in  his  way.  This  photograph  affords  a  good  illustration  of  the  astonishing  thoughtlessness 
or  carelessness  manifested  by  persons  working  about  scaffolds.) 

lower  one,  and  fastened  to  it  by  means  of  cleats  that  are 
securely  nailed  to  both  poles.  These  cleats  should  be  of 
good,  sound  material,  not  less  than  1  1/4  in.  thick,  and 
they  should  be  somewhat  wider  than  the  poles.  They 


FUNCTION  OF  THE  LEDGERS  47 

should  be  not  less  than  four  feet  long,  and  be  placed  so 
that  they  overlap  each  pole  by  not  less  than  two  feet ; 
and  they  should  be  secured  to  the  poles  by  nailing 
with  10-penny  cut  nails,  not  less  than  six  nails  being 
used  to  fasten  -each  cleat  to  each  pole  (The  character 
of  the  nails  is  further  considered  in  paragraph  79.) 

Two  such  cleats  should  be  used  to  every  joint  or 
splice,  and  the  cleats  should  not  be  nailed  to  opposite 
sides  of  the  poles,  but  to  two  adjoining  sides,  so  that 
they  may  lie  at  right  angles  to  each  other,  and  so  pro- 
vide proper  stiffness  and  support  in  every  direction. 
They  must  moreover  be  placed  so  that  they  will  not 
interfere  with  either  the  ledgers  or  the  hand-rails,  which 
are  presently  to  be  described.  The  abutting  ends  of 
the  two  poles  should  also  be  perfectly  square  and  flat, 
so  that  a  good  bearing  may  be  had. 

It  is  highly  desirable  to  "break  joints"  in  erecting 
the  uprights  of  pole  scaffolds.  That  is,  it  is  preferable 
to  avoid  splicing  two  or  more  consecutive  or  contiguous 
uprights  at  the  same  general  level.  This  is  because  a 
splice  or  joint,  as  made  by  nails  and  cleats,  has  but 
little  stiffness  in  comparison  with  the  pole  itself,  and 
hence  by  splicing  alternate  uprights  at  different  levels 
the  scaffold  as  a  whole  is  rendered  much  stiff er,  and  is 
correspondingly  less  likely  to  collapse  through  the 
buckling  of  the  poles. 

THE    LEDGERS 

27.  Function  of  the  Ledgers.  The  ledgers  are  the 
horizontal  stringers  that  run  from  pole  to  pole,  parallel 
to  the  wall  of  the  building.  They  support  the  cross- 
beams or  putlogs  upon  which  the  platform  rests,  and 
transmit  the  weight  of  the  platform,  and  of  whatever 


48  BRICKLAYERS'  POLE  SCAFFOLD 

is  upon  it,  to  the  poles  or  uprights.  They  also  serve 
to  stiffen  the  poles  and  prevent  them  from  bending, 
individually,  in  a  direction  parallel  to  the  wall  (or 
lengthwise  of  the  scaffold) .  They  do  not  prevent  the 
poles  from  all  yielding  simultaneously,  however,  and 
this  fact  must  not  be  forgotten  in  considering  the 
bracing  of  the  scaffold,  which  is  discussed  in  a  subse- 
quent section. 

28.  Material,  Size,  and  Quality.  The  ledgers,  like 
the  poles,  are  preferably  made  of  spruce.  Hemlock 
should  never  be  used,  for  the  reasons  already  given  in 
paragraph  20,  in  discussing  the  poles.  Ledgers  should 
not  be  less  than  1  1/4  in.  thick,  and  it  is  advisable 
to  make  them  12  in.  wide  for  heavy  work,  although  a 
width  of  10  in,  is  sufficient  when  the  load  on  the 
platform  is  sure  to  be  light,  and  the  putlogs  are  kept 
close  to  the  poles,  as  explained  in  paragraph  39. 
Ledgers  as  narrow  as  8  in.  are  often  used,  and  it  must 
be  admitted  that  they  seldom  break  when  they  are 
made  of  first-class  stock  and  not  loaded  heavily;  but 
we  greatly  prefer  a  minimum  width  of  10  in. 

The  length  of  the  ledgers  will  depend  upon  the 
spacing  of  the  poles  to  which  they  are  secured.  When 
the  poles  are  set  at  the  standard  interval  of  7  ft.  6  in. 
between  centers,  the  ledgers  should  be  at  least  16  ft. 
long.  This  allows  them  to  extend  across  two  bays 
(or  two  consecutive  pole-spaces),  and  to  lap  over  the 
poles  by  a  few  inches  at  each  end,  so  that  they  can  be 
properly  nailed. 

The  ledgers  should  be  made  of  material  that  is 
sound  and  first  class  in  every  respect.  They  should 
be  free  from  bad  knots  or  cross-grained  places  or  shakes, 
and  they  should  be  straight  and  flat  and  thoroughly 


RELATION  OF  LEDGERS  TO  POLES  49 

seasoned.  A  winding  (or  twisted)  ledger  cannot  be 
secured  to  the  poles  satisfactorily,  and  an  unseasoned 
one  is  likely  to  warp  and  twist  out  of  shape  while  in  user 
so  as  to  either  start  the  nails  by  which  it  is  held,  or  throw 
a  severe  and  entirely  unnecessary  stress  upon  them. 

Ledgers  are  likely  to  become  badly  split  at  the 
ends  after  they  have  been  used  a  few  times.  (See 
paragraph  33.)  Great  attention  should  be  paid  to  their 
condition  in  this  respect,  and  any  that  are  split  to  a 
serious  extent  should  be  discarded  and  used  thereafter 
for  other  purposes.  Ledgers  should  also  be  rejected 
when  they  have  become  weakened  to  any  material 
extent  by  nail  holes,  even  if  they  are  not  split. 

29.  Relation  of  the  Ledgers  to  the  Poles.  Some 
scaffold  builders  nail  the  ledgers  to  the  inner  sides  of  the 
poles,  while  others  nail  them  to  the  outer  sides,  and 
some  prefer  to  put  them  alternately  inside  and  outside. 
So  far  as  safety  is  concerned,  there  is  some  advantage 
in  nailing  them  to  the  inner  sides  because  the  span  of 
the  putlogs  is  somewhat  less  in  that  case, — the  gain  in 
this  respect  being  5  1/4  in.  when  the  pole  is  4  in.  square 
and  the  ledger  is  1  1/4  in.  thick.  Where  the  scaffold 
turns  a  right  angle  the  ledgers  coming  together  at  the 
corner  pole  cannot  be  secured  to  it  properly  if  both  are 
on  the  inside;  hence  builders  who  prefer  to  run  the 
ledgers  inside  often  spring  one  of  them  so  that  it  runs 
outside  of  the  corner  pole  and  inside  of  the  others. 
When  two  ledgers  meet  at  right  angles  one  of  them  is 
nailed  with  its  end  flush  with  the  pole,  and  the  other 
is  allowed  to  lap  over  in  the  usual  manner.  The  one 
that  stops  flush  with  the  pole  should  be  sawed  off 
truly  square,  so  that  it  may  have  as  full  a  bearing  as 
possible,  and  offer  a  sufficient  area  for  good  nailing. 


50  BRICKLAYERS'  POLE  SCAFFOLD 

30.  Vertical    Spacing    of  Ledgers.     The  distance 
from  any  given  ledger  to  the  one  next  above  it  is  de- 
termined by  the  manner  in  which  the  scaffold  is  used. 
With  the  platform  at  a  given  level,  the  men  lay  the 
wall  until  it  has  reached  a  height  beyond  which  further 
work  would  be  inconvenient.     The  platform  is  then 
raised  so  as  to  rest  upon  another  series  of  ledgers  at  a 
somewhat  higher  level,  and  the  job  progresses  in  this 
way  until  the  wall  is  completed, — all  the  work  of  brick- 
laying being  done  from  a  single  platform,  which  is 
shifted  upward  from  time  to  time,  so  as  to  be  always 
within  a  convenient  distance  of  the  level  at  which  the 
bricks  are  being  set.     The  height  from  the  upper  edge 
of  one  ledger  to  the  upper  edge  of  the  one  next  above 
it,  as  thus  determined,  is  approximately  5  ft.  2  in.     As 
the  platform  is  raised  with  the  progress  of  the  work, 
the  ledgers  upon  which  it  has  rested  at  previous  stages 
are  not  removed,  but  are  left  in  position  to  brace  and 
stiffen  the  poles  against  displacement  in  a  direction 
parallel  to  the  length  of  the  platform. 

31.  Erecting  the  Ledgers.     While  the  bricklayers 
are  at  work  at  one  level,  the  ledgers  that  are  required 
for  the  support  of  the  platform  in  its  next  higher  posi- 
tion are  fixed  in  place.     In  putting  up  a  new  ledger, 
a  furring  strip  or  cleat  is  first    nailed  to  each  pole  to 
support  the  weight  of  the  ledger  until  it  can  be  properly 
nailed  on,  and  to  afford  it  a  certain  measure  of  perma- 
nent support  in  addition  to  that  given  by  its  own  nails. 
There  is  no  standard  size  for  these  cleats  or  strips,  but 
they  should  be  an  inch  or  more  in  thickness,  and  at 
least  two  inches  in  width,  and  10  in.  or  12  in.  long; 
and  each  should  be  secured  to  its  pole  by  several  nails. 
The  ledger  is  next  laid  in  position  against  the  poles 


NAILING  51 

with  its  weight  resting  upon  the  furring  strips,  and  is 
nailed  in  place.  Care  should  be  taken  to  see  that  the 
ledgers  are  level,  and  that  their  top  edges  are  at  the 
same  height  as  the  bottom  of  the  openings  left  in  the 
wall,  opposite  them,  for  receiving  the  ends  of  the  put- 
logs. Care  should  also  be  taken  to  see  that  each  ledger 
overlaps  the  poles  by  the  same  amount  at  each  end, 
so  that  the  final  nailing  may  be  done  equally  well  in 
all  places. 

32.  Nailing.  Each  ledger  should  be  nailed  to  each 
pole  with  five  first-class  10-penny  cut  nails.  The 
8 -penny  size  is  not  large  enough  for  safety.  (The 
quality  of  the  nails  is  considered  in  paragraph  79.) 
Where  two  ledgers  lap  over  each  other  on  the  same  pole, 
the  under  one  should  be  first  nailed  to  the  pole  as  here 
described,  and  the  outer  ledger  should  then  be  nailed 
to  the  under  one  just  as  though  it  were  being  secured 
directly  to  a  pole.  The  nails  should  be  well  distributed 
in  all  cases,  and  none  of  them  should  be  driven  close 
to  the  top  edge  of  a  ledger. 

It  is  easy  for  the  man  who  is  erecting  a  bricklayers' 
scaffold  to  make  serious  mistakes  and  oversights,  even 
though  he  may  know  quite  well  what  the  construction 
ought  to  be,  and  have  every  intention  of  carrying  it 
out  properly.  In  putting  up  a  ledger,  for  example,  it 
is  common  practice  to  tack  one  end  with  a  single  nail, 
just  to  hold  it  in  place  for  the  time  being,  and  then  to 
begin  the  work  of  permanent  nailing  from  the  other 
end.  In  proceeding  in  this  way  the  workman  may 
forget  that  he  has  not  secured  the  first  end  properly, 
thus  leaving  it  with  but  a  single  nail,  which  may  per- 
haps not  even  be  fully  driven  home.  An  oversight 
of  this  kind  is  very  likely  indeed  to  result  in  a  fall, 


52  BRICKLAYERS'  POLE  SCAFFOLD 

when  the  weight  of  the  loaded  platform  comes  upon  the 
defectively  fastened  ledger.  It  is  much  better  to  com- 
plete the  nailing  at  the  first  end  before  proceeding  to 
the  other  end,  or  to  the  middle.  A  final  tentative 
shake,  given  by  the  hand  to  each  end  of  the  ledger 
and  to  its  middle  point,  will  betray  any  omission  that 
may  have  been  made  in  the  nailing,  but  it  would 
probably  fail  to  give  proper  warning  if  some  part  were 
slightly  tacked,  but  not  secured  properly. 

The  man  charged  with  the  erection  of  a  scaffold 
should  never  have  any  other  job  in  hand  at  the  same 
time,  and  while  he  is  engaged  in  the  work  of  erection 
his  attention  should  never  be  drawn  away  from  it  for 
any  reason  whatsoever,  except  for  the  avoidance  of 
some  other  more  imminent  danger. 

One  man  can  do  most  of  the  work  of  erecting  a 
bricklayers'  scaffold  that  is  constructed  in  accordance 
with  American  practice.  He  will  need  assistance  main- 
ly in  raising  the  poles  or  uprights,  and  in  carrying 
the  planks  and  other  needful  materials  to  the  working 
platforms. 

33.  Splitting  of  Ledgers.  When  the  ledgers  are 
nailed  to  the  poles,  as  herein  described,  the  holding 
power  of  the  nails  is  such  that  in  dismantling  the 
scaffold  the  ledgers  are  apt  to  become  badly  split  at 
the  ends.  This  trouble  is  so  common  and  so  marked 
that  the  ledgers  are  often  damaged,  by  once  using  them, 
to  such  an  extent  that  they  should  be  immediately 
discarded.  As  a  result,  builders  of  scaffolds  are 
tempted  to  use  ledgers  that  are  not  in  proper  condition, 
because  of  the  expense  involved  in  procuring  new 
material  for  each  new  job. 

The  splitting  of  the  ledgers  at  the  ends  is  caused 


CLAMPS  53 

mainly  by  unnecessarily  rough  treatment,  the  men 
striking  them  heavily  on  the  back  with  their  hammers, 
to  draw  the  nails.  The  splitting  can  be  reduced  in  large 
measure  by  striking,  not  directly  upon  the  ledger 
itself,  but  upon  a  block  held  against  it.  It  cannot  be 
wholly  prevented  in  this  way,  however. 

Ledgers  can  best  be  removed  from  the  poles  by 
using  a  stirrup-shaped  special  tool  that  can  be  turned 
out  easily  and  quickly  by  any  blacksmith.  To  make 
this  tool,  select  a  bar  of  iron  about  3/4  inch  square 
and  four  feet  or  so  in  length,  and  at  one  end  turn  about 
a  foot  of  it  back  parallel  to  the  main  length  of  the  bar 
so  that  it  lies  at  a  distance  from  it  equal  to,  or  slightly 
exceeding,  the  thickness  of  the  ledger.  In  using  the 


FIG.  11.     A  SPECIAL  TOOL  FOR  REMOVING  LEDGERS  FROM  POLES. 

tool,  catch  the  ledger  to  its  full  width,  and  as  near  to 
the  pole  as  possible,  in  the  V-shaped  space  between 
the  shank  of  the  bar  and  the  turned-over  end,  and 
work  it  loose  by  moving  the  tool  backward  and  for- 
ward. Ledgers  may  be  taken  off,  in  this  way,  with 
little  or  no  splitting,  and  their  usefulness  will  be  corre- 
spondingly prolonged. 

34.  Clamps.  To  lessen  the  damage  to  the 
ledgers  from  nails,  they  are  sometimes  secured  to  the 
poles  by  means  of  clamps.  Various  forms  of  clamps 
have  been  designed  for  this  purpose,  but  none  of  them 
have  come  into  general  use  in  the  United  States.  They 
have  been  applied  here  to  some  extent  in  the  past  few 


54  BRICKLAYERS'  POLE  SCAFFOLD 

years,  however,  and  they  are  quite  widely  used  in 
Germany.  Some  of  them,  in  sparing  the  ledgers, 
damage  the  poles  to  a  corresponding  extent.  One 
form  of  clamp  which  has  been  used  quite  a  little  in 
this  country  is  shown  in  Fig.  12,  from  which  its  con- 
struction and  mode  of  application  can  be  clearly  seen. 


FIG.    12.     A  FORM  OF  LEDGER  CLAMP  IN  USE   BY  AMERICAN 

BUILDERS. 


FUNCTION  OF  THE  PUTLOGS  55 

THE  PUTLOGS 

35.  Function  of  the  Putlogs.     The  putlogs  (also 
known   among  masons    and    builders  as   "putlocks", 
"puds",  or  "cross-bars"),  are  the  horizontal  pieces  that 
run  perpendicularly  to  the  wall  and  afford  direct  and 
immediate  support  to  the  planking  of   the   platform. 
They  occur,  in  one  form  or  another,  in  nearly  all  types 
of  scaffolds.     In  the  American  type  of  the  bricklayers' 
pole  scaffold,  here  under  consideration,  they  are  merely 
short  wooden  beams,  square  or  rectangular   in   cross- 
section,  and  supported  at  one  end  by  the  wall  that  is 
being  laid,   and   at  the  other  by  the    ledgers  of  the 
scaffold. 

36.  Material,  Size,  and  Quality.     Of  the  various 
kinds  of  wood  that  are  available  for  making  putlogs, 
chestnut  is  considered  to  be  the  best,   in  this  country. 
In  England  birch  is  quite  commonly  used,  but  Ameri- 
can practice  does  not  favor  it.     Spruce  is  often  used 
for  putlogs,  and  it  answers  very  well  when   chestnut 
cannot  be  had  conveniently.     The  rapid  spread  of  the 
apparently  incurable  "chestnut  blight"  threatens   the 
extermination  of  the  chestnut  tree,  and  hence    it    is 
probable  that  spruce  will  be  more  and  more  employed 
for  putlogs  as  the  years  go  by. 

In  the  selection  of  material  for  the  putlogs,  great 
care  should  be  taken  to  avoid  pieces  that  are  defective 
or  inferior  in  any  way.  The  wood  should  be  sound 
and  free  from  knots,  and  of  first-class  quality  in  every 
respect.  Special  attention  should  be  paid  to  its 
grain,  which  should  be  straight  and  close.  In  English 
practice  the  putlogs,  when  rectangular  in  section, 
are  usually  split  instead  of  being  sawed,  in  order 


56  BRICKLAYERS'  POLE  SCAFFOLD 

to  avoid  cutting  any  of  the  fibers  upon  the  continuity 
of  which  the  strength  of  the  putlog  depends,  and  also, 
no  doubt,  because  only  good  logs  can  be  split  properly. 
In  Germany,  too,  split  or  hewn  material  is  preferred, 
though  its  use  is  not  mandatory.  There  is  no  need 
of  insisting  that  the  putlogs  be  split,  but  the  attention 
that  has  been  given  to  this  matter  in  other  countries 
will  serve  to  emphasize  the  importance  of  seeing  to  it 
that  the  material  is  sound,  and  perfectly  straight- 
grained. 

Putlogs  should  be  at  least  4  inches  square,  in  the 
bricklayers'  scaffold  as  built  in  the  United  States,  when 
the  load  that  is  to  be  carried  by  the  platform  is  of 
the  usual  nature  and  amount;  and  they  should  be 
correspondingly  larger  if  the  load  to  be  carried  is 
heavier  than  usual.  It  is  common  to  find  putlogs 
having  a  section  3  inches  by  4  inches,  and  while  this 
is  sufficient  in  many  cases,  the  larger  size  is  greatly 
to  be  preferred,  even  for  light  loads. 

The  putlogs  should  be  long  enough  to  project 
over  the  ledgers  by  not  less  than  one  foot.  If  there 
is  a  clear  space  of  4  feet  6  inches  between  the  poles 
and  the  wall  of  the  building,  this  means  that  the  putlog 
should  be  a  little  over  6  feet  in  length. 

37.  Support  of  the  Putlogs.  In  the  bricklayers' 
scaffold,  the  end  of  the  putlog  that  i's  nearest  the  build- 
ing is  usually  supported  directly  by  the  wall  that  is 
being  built.  For  this  purpose  a  brick  is  left  out  of  the 
wall  at  the  proper  place,  and  one  -end  of  the  putlog  is 
inserted  in  the  opening  so  made.  To  make  it  possible 
to  do  this,  the  putlog  is  notched  or  cut  down,  at  the 
end,  so  as  to  be  narrow  enough  in  the  vertical  direction 
to  be  capable  of  entering  the  hole  left  in  the  wall  by 


SUPPORT  OF  THE  PUTLOGS 


57 


the  omission  of  the  brick.  The  notch  should  be  cut 
from  the  upper  side  of  the  putlog,  so  that  the  projection 
that  enters  the  hole  in  the  wall  is  on  the  lower  side. 
This  is  important,  because  there  would  be  considerable 
likelihood  of  the  putlog  splitting,  if  its  bottom  fibers 
were  cut  in  making  the  notch  and  the  projection  sup- 
porting the  weight  were  at  the  top.  The  notch  should 
be  just  deep  enough  to  permit  the  end  of  the  putlog  to 
enter  the  hole  in  the  wall,  and  should  not  extend  into 
the  putlog  for  more  than  4  1/2  or  5  inches,  as  measured 
in  the  direction  of  its  length.  Care  should  be  taken 
to  see  that  the  putlog  enters  the  wall  to  the  full  width 


FIG.  13.     CORRECT  POSITION 
OF  PUTLOG. 


FIG.  14.     INCORRECT  POSITION 
OF  PUTLOG. 


of  one  brick  (or  say  4  inches),  but  it  should  not  be  al- 
lowed to  enter  to  a  greater  distance  than  this. 

When  the  wall  that  is  to  be  built  has  many  window 
openings,  it  often  happens  that  one  of  them  comes  at 
a  point  where  a  putlog  would  naturally  be  placed. 
In  this  case  it  is  common  to  arrange  some  form  of 
support  within  the  window  space,  to  hold  up  the  end 
of  the  putlog.  A  piece  of  stout  plank,  set  vertically, 
and  resting  solidly  upon  the  bottom  of  the  window 
opening  or  upon  some  other  secure  foundation,  may  be 


58  BRICKLAYERS'  POLE  SCAFFOLD 

used ;  but  every  care  should  be  taken  to  brace  this  plank 
so  securely  that  it  will  be  comparable  in  solidity  to  the 
wall  itself.  It  should  be  made  secure  against  every 
possible  kind  of  displacement, — against  tipping,  either 
in  or  out  or  side  wise,  and  against  the  displacement  of  its 
lower  end  in  any  manner. 

38.  Security  of  Putlogs.  In  Great  Britain  and 
in  continental  Europe  it  is  customary  to  lash  the  putlogs 
to  the  ledgers  with  metal  cord  or  small  rope,  or  to  fasten 
them  with  clamps ;  but  in  the  United  States  the  putlogs 
are  usually  permitted  to  rest  upon  the  ledgers  without 
being  secured  in  any  way,  it  being  here  considered  that 
the  weight  upon  the  platform  is  sufficient  to  prevent 
the  putlogs  from  becoming  displaced,  either  at  the 
ledgers  or  at  the  wall.  It  might  appear  that  this  prac- 
tice could  not  be  approved  by  the  conservative  safety 
engineer,  but  experience  has  shown  that  there  are  few 
accidents  that  are  traceable  to  the  displacement  of  the 
putlogs,  except  as  this  may  have  occurred  in  conse- 
quence of  inadequate  or  improper  bracing,  or  of  other 
errors  of  construction  or  practice  for  which  the  putlogs 
are  in  no  way  responsible.  The  putlogs,  where  they 
enter  the  wall,  are  sometimes  secured  by  wedges,  but 
this  is  not  at  all  common.  (See  paragraph  153.) 

Putlogs  having  a  cross-section  differing  from  the 
square  form  to  any  marked  extent  should  not  be  used 
unless  they  are  secured  in  some  safe  way,  or  have  broad 
flat  sides  where  they  rest  upon  the  ledgers.  The  put- 
logs of  Europe  which  are  lashed  to  the  ledgers  are 
often  round  in  section,  and  the  lashing  is  therefore 
highly  important ;  but  those  that  we  use  have  a  square 
or  rectangular  section  and  are  therefore  far  more  stable. 
If  unsecured  putlogs  of  rectangular  cross-section  are 


LOCATION  OF  PUTLOGS  59 

employed,  with  a  height  considerably  greater  than  their 
width  (as  would  be  the  case  when  using  planks  turned 
up  edgewise),  there  is  danger  of  the  platform  being 
unstable  or  unsteady,  from  the  tendency  of  the  putlogs 
to  cant  over  upon  their  sides.  It  may  not  be  possible 
for  them  to  turn  completely  over,  on  account  of  the 
restraining  influence  of  the  wall  upon  their  ends;  but 
they  may  nevertheless  be  capable  of  turning  to  some 
considerable  extent,  and  a  sudden  disturbance  of  the 
platform  from  this  cause  might  easily  throw  the  work- 
men off  their  feet  and  lead  to  a  serious  accident. 

39.  Location  of  Putlogs.  There  should  be  at  least 
three  putlogs  under  every  plank  of  the  platform,— 
one  at  each  of  the  respective  ends  of  the  plank  and  one 
in  the  middle.  By  adhering  to  the  general  proportions 
and  dimensions  that  are  recommended  in  this  book  for 
the  parts  of  the  scaffold,  it  is  easy  to  conform  to  this 
condition. 

As  it  is  through  the  putlogs  that  the  load  upon 
the  platform  of  the  scaffold  is  transmitted  to  the 
ledgers,  it  is  important  to  place  them  so  that  they  rest 
upon  the  ledgers  as  closely  to  the  poles  as  possible,  in 
order  to  keep  the  bending  stresses  upon  the  ledgers 
small.  It  may  sometimes,  be  necessary,  in  spacing  the 
putlogs  properly,  to  place  one  or  more  of.  them  at  a 
little  distance  from  the  nearest  pole ;  but  the  importance 
of  transmitting  the  load  to  the  poles  very  directly  and 
immediately  should  be  borne  in  mind  continually, 
and  no  departure  from  this  principle  should  be  per- 
mitted without  good  and  sufficient  reason. 

Care  should  be  taken  to  have  the  putlogs  truly 
level, — this  being  insured  by  the  proper  placing  of  the 
ledgers,  rather  than  by  adjusting  the  putlogs  them- 


60  BRICKLAYERS'  POLE  SCAFFOLD 

selves.  With  the  usual  form  of  putlog  the  top  of  the 
ledger  should  come  directly  opposite  the  bottom  of 
the  hole  in  the  wall  into  which  the  putlog  is  to  enter. 
The  putlogs  should  also  be  placed  as  nearly  square 
to  the  wall  as  possible,  because  this  gives  the  best 
distribution  of  the  stresses  that  are  produced  in  the 
scaffold  by  the  load  on  the  platform,  and  also  affords 
the  best  support  to  the  platform  planks  themselves. 

40.  Treatment  of  Corners.     Where  the  scaffold 
turns   a  corner,   one   or  two  putlogs  should  be   laid 
diagonally  across  the  corner,  so  that  each  may  have 
one  of  its  ends  resting  upon  each  of  the  two  ledgers 
that  meet  at  the  corner.     In  placing  a  putlog  in  this 
way  it  is  better  not  to  run  it  at  an  angle  of  45  degrees 
with  the  ledgers,  because  unless  the  putlog  is  unusually 
long  that  would  leave  both  of  its  ends  at  a  considerable 
distance  from  any  pole.     It  is  better  to  have  one  end 
of  it  near  the  corner  pole,  letting  the  other  end  come 
at  such  distance  from  the  pole  as  may  be  necessary 
in  order  to  accommodate  the  planking.     This  point  is 
more  fully  explained  in  paragraph  45,  in  discussing 
the  platform  of  the  scaffold. 

41.  Special  Forms   of  Putlogs.     At  the  present 
time  walls  are  often  laid  with  wide  intervals  between 
the  rows  of  brick,  a  space  of  5/8  inch  being  more  or  less 
common.     This  has  led  to  the  devising  of  forms  of 
putlogs  that  enable  the  builder  to  erect  a  bricklayers' 
scaffold  without  leaving  out  bricks  here  and  there  for 
the  support  of  the  platform.     In  one  of  these  special 
designs  the  putlog  is  of  the  usual  shape  and  dimensions, 
but  instead  of  being  notched  at  the  end  it  is  fitted  there 
with  a  sort  of  shoe  consisting  of  two  pieces  of  sheet 
steel,  each  about  1/4  inch  in  thickness.     One  of  these 


SPECIAL  FORMS  OF  PUTLOGS 


61 


FIG.  15.     A  SPECIAL  PUTLOG  FOR  USE  ON  WALLS  WITH  WIDELY- 
SPACED  BRICKS. 

pieces  is  straight  and  lies  along  the  bottom  of  the  putlog, 
while  the  other  is  bent  at  right  angles  twice,  so  that 
it  lies  along  the  top  of  the  putlog  for  a  distance  of 
8  inches  or  so,  then  passes  down  over  the  end  of  it, 
and  finally  turns  again  in  the  direction  of  the  length 
of  the  putlog  and  follows  snugly  along  the  bottom 
part  of  the  shoe,  projecting  out  beyond  the  end  of 
the  putlog  to  a  distance  of  not  more  than  4  1/2  or 
5  inches.  The  two  strips  of  steel  are  bolted  together 
solidly  by  bolts  passing  vertically  through  the  putlog, 


FIG.   16.     A  SPECIAL  PUTLOG  FOR  USE  ON  ORDINARY  WALLS. 

(The  lower  edge  of  the  projecting  steel  tongue  should  be  exactly  parallel  with  the  length 
of  the  putlog.  Note  that  in  the  illustration  the  tongue  has  been  forced  upward,  by  use, 
until  it  would  bear  against  the  brickwork  only  at  a  single  point,  close  to  the  putlog.) 


62  BRICKLAYERS'  POLE  SCAFFOLD 

and  their  free  ends  should  also  be  united  by  countersunk 
rivets.  In  using  this  form  of  putlog  the  projecting 
steel  tongue  is  laid  upon  the  wall  in  the  usual  way,  but 
it  is  not  necessary  to  omit  a  brick  for  its  accommoda- 
tion, because,  with  the  wide  spacing  of  the  bricks,  there 
is  room  for  the  tongue  between  two  successive  rows. 
Another  form  of  putlog,  which  is  also  designed  to 
do  away  with  the  temporary  omission  of  bricks  from 
the  wall,  is  shown  in  Fig.  16.  The  essential  feature  of 
this  is  the  sheet  steel  tongue  which  projects  at  the  end, 
and  which,  when  the  putlog  is  in  position,  rests  edge- 
wise upon  the  wall  in  the  vertical  space  between  the 
ends  of  two  successive  bricks.  The  tongue  is  held  in 
place  by  two  bolts  which  pass  through  a  steel  strap 
that  incloses  the  end  of  the  wooden  part  of  the  putlog. 
This  strap  is  a  highly  important  element  in  the  design, 
because  if  it  were  not  present  the  stresses  that  come 
upon  the  bolts  that  hold  the  tongue  would  be  likely 
to  split  the  putlog  and  let  the  platform  down. 

THE    PLATFORM 

42.  Material,  Size,  and  Quality  of  Platform 
Planks.  The  platform  consists  of  planks  laid  directly 
upon  the  putlogs,  and  running  parallel  with  the  wall  of 
the  building.  The  planks  are  usually  made  of  spruce, 
and,  like  all  other  parts  of  the  scaffold,  they  should 
be  of  carefully  selected  material,  straight-grained, 
sound,  and  free  from  bad  knots  or  other  imperfections. 
They  should  never  be  made  of  hemlock,  because,  as 
already  explained,  this  wood  is  likely  to  break  short 
off  without  warning  when  heavily  loaded,  and  it 
sometimes  fails  when  there  appears  to  be  no  adequate 
reason  for  failure.  The  size  of  platform  planks  varies 


WIDTH  OF  PLATFORM  63 

somewhat  in  different  parts  of  the  country.  In  New 
York  they  are  supposed  to  be  16  feet  long,  9  inches  wide, 
and  2  inches  thick.  This  size  is  not  prescribed  by  any 
law  or  ordinance,  but  it  is  established  as  a  sort  of 
trade  standard,  among  builders.  The  spacing  of  the 
poles  and  the  putlogs,  as  herein  recommended,  is  based 
upon  the  use  of  planks  16  feet  in  length,  and  if  shorter 
ones  are  used  the  poles  and  putlogs  must  be  set  corre- 
spondingly nearer  together.  Planks  less  than  2  inches 
thick  are  not  recommended  for  platforms  that  are  to  be 
used  for  laying  brick.  In  England  the  platform  planks 
are  frequently  bound  with  hoop-iron  at  the  ends,  to 
prevent  splitting.  This  is  seldom  done  in  the  United 
States,  and  it  is  doubtful  if  it  is  really  the  best  possible 
practice,  because  the  hoop -iron  is  likely  to  become 
loosened  or  broken  with  service,  and  injuries  to  the  work- 
men from  tripping,  or  from  the  cutting  of  their  hands 
or  feet  by  the  loose  ends  or  edges,  are  likely  to  result. 
43.  Width  of  Platform.  When  9-inch  planks  are 
used,  five  of  them  are  commonly  laid  side  by  side  to 
form  the  floor  of  the  platform.  When  this  arrange- 
ment is  adopted,  and  the  poles  are  set  so  as  to  leave 
a  clear  space  of  4  ft.  6  in.  between  their  inner  surfaces 
and  the  face  of  the  wall,  nine  inches  of  the  length  of 
each  putlog,  inside  of  the  poles,  will  not  be  covered  by 
planking.  The  planks  should  be  so  placed  that  some 
part  of  this  nine  inches  comes  between  the  wall  and  the 
inner  edge  of  the  platform.  The  space  so  left  should  be 
wide  enough  to  enable  the  workman  to  reach  parts  of 
the  wall  that  are  a  few  inches  below  the  floor  of  the 
platform,  but  it  should  never  be  wide  enough  to  become 
a  source  of  danger  from  the  fall  of  materials  or  tools, 
nor  (in  extreme  cases)  of  persons. 


64  BRICKLAYERS'  POLE  SCAFFOLD 

The  planks  of  the  platform  should  be  laid  with 
their  edges  close  together,  so  that  the  platform  will 
be  " tight",  and  have  no  spaces  through  which  small 
tools  or  fragments  of  materials  can  fall. 

In  parts  of  the  country  in  which  the  standard 
platform  plank  is  other  than  nine  inches  wide,  the 
number  of  planks  that  must  be  laid  side  by  side  to 
form  the  platform  will  naturally  be  greater  or  less  than 
five.  The  actual  width  of  the  floor  of  the  platform 
should  be  about  four  feet  in  any  case,  and  it  should 
never  be  enough  greater  than  this  to  require  the  poles 
or  uprights  of  the  scaffold  to  be  set  further  from  the 
wall  than  the  standard  4  feet  6  inches. 

44.  Support  of  the  Planking  by  the  Putlogs. 
The  platform  planks  are  not  nailed  to  the  putlogs, 
nor  secured  to  them  in  any  manner.  It  is  neces- 
sary to  raise  the  platform  at  intervals,  as  described 
in  paragraph  46;  and  the  repeated  driving  and  with- 
drawing of  nails  would  consume  a  great  deal  of  time, 
and  would  also  damage  both  the  planks  and  the  put- 
logs, so  that  they  would  soon  become  weakened  and 
unfit  for  use.  The  platform  might  be  lashed  in  place 
with  rope  or  wire,  or  it  might  be  secured  by  appropriate 
clamps ;  but  experience  has  shown  that  there  should  be 
no  need  of  fastening  the  planks  in  any  way,  if  the  scaf- 
fold is  built  in  faithful  accordance  with  the  principles 
laid  down  in  this  manual.  The  weight  of  the  planks, 
together  with  that  of  the  load  upon  them,  is  sufficient, 
under  these  conditions,  to  prevent  displacement  when 
the  scaffold  is  properly  used. 

Special  care  should  be  taken  to  lay  the  planks  so 
that  they  cannot  tip  up,  either  from  workmen  stepping 
upon  unsupported  ends,  or  from  materials  being  de- 


SUPPORT  OF  THE  PLANKING  65 

posited  upon  the  platform  at  any  point.  In  con- 
formity with  this  principle,  the  planking  should  no- 
where be  allowed  to  project  more  than  one  foot 
beyond  the  last  putlog,  at  any  free  end  of  the  scaf- 
fold platform. 

Where  two  successive  lengths  of  planking  meet, 
they  should  never  be  allowed  to  abut  upon  a  putlog, 
end  to  end,  because  a  slight  shift  of  either  plank  would 
then  be  likely  to  lead  to  an  accident.  Platform  planks 
are  often  laid  end  to  end  in  England,  but  they  are  not 
allowed  to  abut  upon  the  same  putlog.  Two  parallel 
putlogs,  set  about  four  inches  apart,  are  provided  in 
such  cases,  one  supporting  one  of  the  planks  and  the 
other  supporting  the  other  one. 

The  arrangement  of  the  planking  where  the  plat- 
form of  a  bricklayer's  scaffold  turns  a  corner  is  con- 
sidered in  paragraph  45.  At  all  other  parts  of  the 
platform  there  should  be  at  least  three  putlogs  under 
every  plank,— -one  near  each  end  of  the  plank,  and  one 
at  or  near  its  middle  point.  This  condition  can  be 
fulfilled  very  easily,  when  16-foot  planks  are  used  and 
the  poles  of  the  scaffold  are  set  71/2  feet  apart.  Each 
plank  will  then  be  twelve  inches  longer  than  the  dis- 
tance from  the  middle  of  any  one  pole  to  the  middle  of 
the  second  pole  beyond ;  and  if  a  putlog  is  set  at  every 
pole,  each  plank  can  therefore  be  laid  so  that  it  will 
have  a  putlog  under  its  middle  point,  and  will  also 
project,  at  both  ends,  six  inches  beyond  the  center 
lines  of  other  putlogs.  The  planks  should  never  over- 
lap the  center  lines  of  the  putlogs  by  less  than  six 
inches,  and  care  should  be  taken  to  space  the  putlogs 
uniformly  and  correctly,  and  to  see  that  each  plank 
overlaps  by  equal  amounts  at  both  its  ends. 


66  BRICKLAYERS'  POLE  SCAFFOLD 

When  one  section  of  planking  has  been  laid  upon 
the  putlogs  in  this  manner,  the  next  section  is  allowed 
to  rest  upon  the  first  one,  and  so  the  platform  is  con- 
tinued,— the  first,  third,  and  fifth  sections  resting 
directly  upon  the  putlogs,  and  serving,  at  the  same  time, 
to  support  the  second  and  fourth  sections.  The 
general  scheme  of  this  arrangement  will  be  understood 
by  reference  to  Fig.  17,  in  which  the  planks  composing 


FIG.    17.     USUAL  ARRANGEMENT   OF   THE    PLATFORM   PLANKS. 

the  platform  are  seen  to  lie  on  two  different  levels,— 
every  other  length  resting  upon  the  putlogs,  while 
the  intervening  lengths  stand  higher  by  the  thickness 
of  a  plank.  Some  builders  prefer  the  plan  suggested  in 
Fig.  18,  however,  where  each  length  of  planking  rests 
directly  upon  a  putlog  at  one  end,  and  upon  the  pre- 
viously-laid planking  at  the  other  end.  In  either  case, 
each  course  of  planking  will  overlap  the  next  one  by 


FIG.  18.     ANOTHER   METHOD    OF   LAYING   THE    PLANKS. 

twelve  inches,  since  each  overlaps  the  center  line  of  the 
putlog  by  six  inches. 

Every  plank  should  rest  firmly  upon  the  putlogs, 
or  upon  other  planks,  at  all  points  where  it  is  designed 
to  be  supported.  If  this  condition  is  not  fulfilled,  the 
load  upon  the  platform  will  not  be  properly  distributed 
to  the  poles ;  and  the  planks  will  also  spring  and  yield, 
so  that  the  footing  will  be  uncertain,  and  accidents  may 
result.  The  support  of  the  planking  should  receive 


TREATMENT  OF  CORNERS  67 

special  attention  at  the  middle  of  the  courses  that  are 
elevated  by  resting  upon  other  planks.  At  every  such 
point  (see  A,  in  Fig.  19),  a  putlog  of  extra  depth  should 
be  used,  or  else  a  strip  should  be  tacked  to  the  top  of  an 
ordinary  putlog,  of  just  the  right  thickness  to  compen- 
sate for  the  slight  elevation  of  the  plank  at  this  point. 
45.  Treatment  of  Corners.  Where  a  bricklayer's 
pole  scaffold  turns  a  corner,  special  attention  should 
be  paid  to  the  arrangement  of  planks  that  form 
the  flooring.  As  already  explained  in  paragraph  40,  the 
putlog  that  is  to  support  the  planking  at  the  corner 
should  not  be  set  at  an  angle  of  45  degrees,  but  should 
be  placed  so  that  it  will  rest  upon  one  of  the  ledgers 
at  a  point  near  the  corner  pole,  and  upon  the  other 


A'' 

FIG.  19.     SHOWING   THE    NEED   OF   SPECIAL  TREATMENT   AT 
CERTAIN  POINTS. 

ledger  (that  runs  at  right  angles  to  the  first  one)  at  a 
point  near  to  the  first  pole  from  the  corner, — the  poles 
near  the  corner  of  the  scaffold  being  set  closer  together 
than  elsewhere,  so  that  the  putlog  that  is  set  in  the 
diagonal  position  need  not  be  materially  longer  than 
the  ones  that  are  used  to  support  the  straight  parts 
of  the  platform.  The  diagonally -placed  putlog,  when 
located  as  here  described,  will  make  a  sharp  (or  acute) 
angle  with  one  of  the  ledgers,  and  a  blunt  (or  obtuse) 
angle  with  the  other  one.  In  laying  the  flooring  of  the 
platform,  the  planks  that  meet  the  putlog  most  nearly 
at  a  right  angle  should  be  laid  first,  and  these  should 
extend  over  the  diagonally-placed  putlog  far  enough  to 
have  a  good,  firm,  safe  bearing,  but  not  far  enough  to 


68 


BRICKLAYERS'  POLE  SCAFFOLD 


FIG.  20.     SHOWING  THE  CORNER  PUTLOG  IN  POSITION. 


FIG.  21.     SHOWING  THE  FIRST  COURSE  OF  PLANKS  IN  POSITION. 


Sfl 


FIG.  22.     SHOWING  BOTH  COURSES  OF  PLANKING  IN  POSITION. 


SHIFTING  THE  PLATFORM  69 

involve  any  danger  from  tipping,  if  a  workman  should 
step  upon  the  projecting  ends. 

The  first  layer  of  planks  having  been  laid  in  this 
manner,  so  that  one  of  the  platforms  has  been  carried 
up  to,  and  across,  the  corner  of  the  scaffold,  the  other 
platform,  running  at  right  angles  to  the  first  one, 
should  next  be  laid,  and  its  planks  should  extend  over 
and  entirely  across  the  first  layer.  Any  load  that  may 
be  thrown  upon  the  second  (or  upper)  platform  near  its 
end  is  then  transferred  to  the  lower  one,  and  from  this 
to  the  putlog  that  has  been  set  diagonally  at  the  corner. 

The  arrangement  here  recommended  for  the  putlog 
and  planking  is  clearly  shown  in  Figs.  20  to  22. 

46.  Shifting  the  Platform.  Whenever  the  wall 
that  is  being  laid  has  risen  to  a  certain  height 
above  the  platform — about  five  feet,  under  ordinary 
circumstances, — the  bricklayers  communicate  with  the 
men  who  are  charged  with  the  erection  of  the  scaffold, 
and  give  notice  that  they  are  ready  to  have  the  platform 
raised.  New  ledger  boards  have  been  nailed  to  the 
poles,  at  the  proper  height,  before  this  time,  and  when 
the  word  to  raise  the  platform  has  been  given,  the  first 
step  is  to  set  the  putlogs  that  are  to  support  the  plat- 
form in  its  new  position.  The  platform  that  is  to  be 
shifted  should  be  left  undisturbed  until  the  new  putlogs 
have  been  put  in  place,  and  a  sufficient  number  of  extra 
putlogs  should  be  provided,  to  make  it  possible  to  do 
this.  It  is  not  good  practice  to  take  putlogs  from  under 
the  middle  of  the  planks  of  the  old  platform,  to  use  in 
erecting  the  new  course  at  the  higher  level;  but  in 
placing  the  new  putlogs,  it  is  convenient  to  temporarily 
omit,  from  the  new  platform,  the  ones  that  will  even- 
tually be  required  under  the  middle  points  of  the  planks, 


70  BRICKLAYERS'  POLE  SCAFFOLD 

— the  putlogs  that  are  to  support  the  ends  of  the  planks 
being  laid  first,  and  the  middle  ones  being  left  out  until 
the  new  platform  is  otherwise  complete,  or  nearly  so. 
By  this  means  the  shifting  of  the  platform  planks  to  the 
upper  level  is  considerably  facilitated,  and  there  is  no 
sacrifice  of  safety,  provided  the  middle  putlogs  are  not 
forgotten  and  omitted  permanently.  This  is  not  likely 
to  occur,  because  the  spring  of  the  newly-laid  planking 
would  betray  the  absence  of  these  putlogs. 

The  putlogs  for  supporting  the  ends  of  the  planks 
of  the  new  platform  being  in  position,  the  planks  them- 
selves are  next  passed  up  and  laid  in  place.  In  doing 
this  it  is  best  to  leave  at  least  one  undisturbed  line  of 
planking  along  the  entire  length  of  the  old  platform 
until  the  rest  of  the  platform  planks  have  been  shifted 
to  their  new  positions ;  and  it  is  advisable  to  have  extra 
planks  at  hand,  so  that  the  new  platform  may  be  laid 
complete,  even  to  the  placing  of  the  putlogs  under  the 
middle  points  of  its  planks,  before  the  last  line  of  plank- 
ing is  removed  from  the  old  platform.  Attention  to 
this  point  will  materially  reduce  the  dangers  to  which 
the  men  erecting  the  scaffold  are  exposed. 

When  the  platform  has  been  shifted  to  its  new  level 
as  here  described,  any  planks  that  still  remain  at  the 
old  level  are  removed,  and  the  old  putlogs  are  taken 
away.  Attention  is  then  given  to  such  additional 
bracing  as  the  increase  in  the  height  of  the  structure 
may  call  for,  and  also  to  the  hand-rails  and  foot- 
boards, as  described  in  subsequent  sections,  below. 

BRACING 

47.  General  Considerations.  Pole  scaffolds  re- 
quire bracing  not  only  to  insure  a  sufficient  de- 


BRACING  71 

gree  of  stiffness  in  the  scaffold  itself,  but  also  to 
prevent  the  scaffold  from  falling  away  from  the  build- 
ing, as  a  whole  J 

The  splices  in  the  uprights  have  but  little  strength 
for  resisting  bending  stresses,  when  the  successive  poles 
are  placed  one  over  another  with  their  ends  abutting. 
This  fact  should  be  carefully  recognized,  and  the  struc- 
ture should  be  braced  and  supported  in  such  a  way  that 
the  only  stress  thrown  upon  a  pole  at  a  splice  is  the 
direct  vertical  thrust  that  is  due  to  the  weight  of  the 
scaffold  and  its  load.  Moreover,  in  a  high  scaffold 
the  poles  should  be  stiffened  by  braces,  even  if  they  are 
continuous  and  free  from  splices;  for  without  braces 
they  would  be  in  the  condition  of  long,  thin  columns 
subject  to  an  endwise  thrust,  and  they  would  therefore 
be  structurally  weak,  and  if  the  load  were  at  all  heavy 
they  would  be  in  danger  of  failing  by  springing  at  their 
middle  points.  (See  Fig.  23 .)  This  danger  is  increased 
by  the  presence  of  the  splices,  and  by  the  fact  that 
the  poles  are  seldom  exactly  straight,  even  when  special 
efforts  have  been  made  to  have  them  so. 

It  should  also  be  remembered  that  it  is  possible 
for  the  scaffold  to  fall  down  bodily, — not  by  the  failure 
of  its  poles,  but  by  swinging  away  from  the  building 
as  a  whole,  and  turning  about  the  lower  ends  of  the 
supporting  poles  as  a  door  turns  upon  its  hinges. 
(See  Fig.  24.)  It  may  also  collapse  by  moving  parallel 
to  the  wall  of  the  building, — the  scaffold  folding  up  as  it 
falls,  and  the  poles  going  down  like  a  row  of  dominoes. 
(See  Fig.  25.)  f*To  guard  against  failure  by  either  of 
these  methods  it  is  important  to  have  the  scaffold 
properly  stiffened  and  braced,  not  only  by  tying  its 
parts  together,  but  also  by  securing  the  whole  structure 


72 


BRICKLAYERS'  POLE  SCAFFOLD 


I- 


FIG.  23.     FAILURE  BY  THE  BUCKLING  OF  THE  POLES. 


ru—: — »:^ 


FIG.  24.     FAILURE  BY  FALLING  AWAY  FROM  THE  BUILDING. 


i    M     /i     Ik     /!     / 


FIG.  25.     FAILURE  BY  COLLAPSING  PARALLEL  TO  THE  WALL. 


BRACING  73 

to  the  building  that  is  being  constructed,  or  to  some 
other  fixed  and  solid  object  J. 

'In  determining  the  number  of  braces  that  are  to  be 
used  in  stiffening  a  scaffold,  careful  attention  should  be 
paid  to  the  character  of  the  scaffold  and  to  the  service 
that  is  expected  of  it.  A  scaffold  that  is  to  extend  to  a 
considerable  height,  and  which  is  likely  to  be  loaded  at 
times  with  a  considerable  amount  of  material,  should  be 
braced  much  more  thoroughly  and  substantially  than 
may  be  necessary  in  one  that  is  to  extend  only  to  a 
moderate  height  and  that  will  be  loaded  only  lightly,,  j 
Care  should  be  taken,  however,  to  err  on  the  safe  side, 
and  to  increase  and  strengthen  the  bracing  in  every 
case  in  which  there  is  the  least  doubt  of  its  adequacy. 

Braces  that  are  put  up  for  the  purpose  of  holding 
the  scaffold  at  a  proper  distance  from  the  wall  should 
always  be  secured  to  the  ledgers  very  near  to  the  poles, 
or  to  the  poles  themselves.  If  they  are  attached  to 
the  ledgers  midway  between  the  poles,  the  support 
that  is  afforded  is  much  less  secure,  because  the  flexi- 
bility of  the  ledgers  will  allow  the  scaffold  to  move  to 
a  considerable  extent  before  the  full  supporting  effect 
of  the  braces  can  be  realized. 

Braces  of  inferior  material  and  of  too  small  a  size 
are  often  used  to  stiffen  or  support  scaffolds.  This  is  a 
serious  mistake.  The  material  should  be  of  first-class 
quality  in  every  respect,  and  the  braces  should  be  large 
enough  to  safely  carry  any  stress  that  they  could  be 
called  upon  to  bear,  even  under  the  most  unusual  cir- 
cumstances. The  ends  of  the  braces  should  also  be 
secured  in  a  thoroughly  workmanlike  manner,  and  with 
a  sufficient  number  of  nails  of  the  quality  indicated 
in  paragraph  79.  It  should  always  be  remembered, 


74  BRICKLAYERS'  POLE  SCAFFOLD 

too,  that  the  stress  may  be  either  a  tension  or  a  thrust, 
and  the  braces  should  be  designed  and  proportioned 
accordingly. 

48.  Bracing  at  Window  Openings.  To  stiffen 
the  scaffold,  and  to  prevent  it  from  falling  over  as  a 
whole,  it  should  be  attached  to  the  building  at  many 
points,  and  in  a  most  effective  manner.  At  the  level 
of  the  working  platform  the  putlogs  are  supposed  to  tie 
the  scaffold  to  the  wall  with  sufficient  security,  and 
there  is  seldom  any  trouble  on  this  score  if  the  putlogs 
are  correct  in  form,  and  properly  put  in  place,  and  carry- 
ing their  normal  load.  Putlogs  have  no  value  as  braces, 
however,  unless  they  are  loaded;  for  they  are  seldom 
fastened  in  any  way,  either  to  the  ledgers  or  to  the 
building,  and  their  effectiveness  in  holding  the  scaffold 
to  the  wall  depends  solely  upon  their  friction  against 
the  ledgers  and  the  brickwork. 

When  the  wall  beside  the  scaffold  contains  a  con- 
siderable number  of  window  openings,  braces  may  be 
run  to  these  openings  from  the  poles  of  the  scaffold. 
At  their  outer  ends,  these  braces  are  to  be  securely 
fastened  to  the  poles.  At  their  inner  ends  they  may 
be  attached  to  the  window  frames,  but  if  the  floors  are 
carried  up  sufficiently  to  make  such  a  course  possible, 
it  is  much  better  to  run  the  braces  through  the  windows, 
fastening  them  to  the  joists  of  the  floors  inside,  or  to  the 
flooring  itself.  In  such  cases  it  is  well  to  nail  them  to 
the  window  frames  also,  because  greater  stiffness  is 
secured  in  this  way;  but  it  is  not  the  best  practice  to 
attach  them  to  the  window  frames  alone,  if  use  can  be 
made  of  the  flooring  also.  When  reliance  is  placed 
mainly  upon  window  braces,  every  window  opening 
should  receive  at  least  one  or  two  or  them ;  for  although 


SHORING  75 

the  support  that  is  thus  provided  will  sometimes  be 
insufficient,  there  a, re  few  cases  in  which  it  will  be  at  all 
excessive.  In  fact,  additional  bracing  of  some  other 
form  should  be  used,  in  any  event,  unless  the  windows 
are  numerous  and  close  together,  and  are  spaced  at 
fairly  uniform  distances. 

If  the  window  braces  are  set  obliquely  to  the  wall, 
with  half  of  them  running  in  one  direction  and  half  in 
the  other,  they  will  serve  not  only  to  hold  the  scaffold 
at  the  right  distance  from  the  wall,  but  also  to  stiffen 
it  considerably  in  a  lengthwise  direction,  so  as  to  prevent 
it  from  collapsing  by  turning  about  the  ends  of  its  own 
poles,  in  a  direction  parallel  to  the  wall.  (See  Fig.  25.) 

49.  Shoring.  When  the  window  openings  are 
few  in  number,  or  when  the  floors  are  not  laid  rapidly 
enough  to  remain  at  all  times  within  a  short  distance 
of  the  scaffold  platform,  it  is  often  necessary  to  employ 
some  form  of  bracing  other  than  the  window  bracing 
described  in  the  preceding  paragraph.  If  the  outer 
edge  of  the  scaffold  stands  near  to  another  building  that 
has  been  previously  erected,  shores  for  the  support  of 
the  scaffold  can  often  be  run  between  the  new  wall  and 
the  old  one.  In  the  absence  of  any  such  convenient 
building,  shores  can  also  be  run  from  the  scaffold  to 
the  ground,  in  some  cases,  although  this  method  of 
bracing  is  seldom  practicable  except  for  the  lower 
levels  of  the  scaffold.  Moreover,  shores  running  to  the 
ground  are  usually  in  the  way  of  the  workmen,  and 
they  are  also  likely  to  be  disturbed  by  teams,  or  by 
beams  or  other  materials  that  are  being  hoisted  or 
shifted  about. 

When  shores  are  used,  and  whether  they  rest 
against  another  building  or  against  the  ground,  the 


76  BRICKLAYERS'  POLE  SCAFFOLD 

scaffold  poles  that  they  support  should  be  kept  away 
from  the  wall  by  the  use  of  struts  of  the  proper  size 
and  length,  so  that  the  poles  cannot  be  forced  toward 
the  wall  by  the  weight  of  the  shores,  or  from  any  other 
cause.  For  scaffold  work,  shoring  is  decidedly  inferior 
to  other  methods  of  bracing,  and  it  should  be  adopted 
only  when  the  other  available  methods  are  open  to 
serious  special  objections.  As  a  rule,  spring  stays  are 
greatly  preferable,  if  they  are  put  up  in  a  workmanlike 
manner. 

50.  Spring  Stay  Braces.  The  spring  stay,  which 
is  widely  used  for  bracing  scaffolds  to  their  walls,  con- 
sists of  a  pair  of  boards  not  wider  than  the  length  of  a 
brick,  and  set  so  as  to  run  from  one  of  the  putlog  holes 
that  are  left  in  the  wall  as  the  scaffold  goes  up,  to  the 
pole  or  ledger  opposite  this  putlog  hole.  It  is  put  in 
position  after  removing  the  putlog,  in  raising  the  plat- 
form to  a  higher  level.  The  ends  of  both  boards  are 
thrust  into  the  putlog  hole  as  far  as  they  will  go  (which 
should  not  be  less  than  the  width  of  a  brick).  A  brick 
is  then  laid  between  the  two,  after  which  their  outer 
ends  are  brought  forcibly  together,  and  nailed  to  the 
ledger.  This  causes  the  inner  ends  of  the  boards  to 
press  against  the  upper  and  lower  surfaces  of  the 
putlog  hole  so  powerfully  that  the  brace  cannot  be 
pulled  out  without  the  exertion  of  a  very  considerable 
force.  The  boards  that  are  used  should  be  sound  and 
perfect  in  all  respects,  and  the  brace  should  be  nailed 
to  the  ledger  close  to  one  of  the  poles,  in  order  to 
obtain  as  stiff  a  construction  as  possible.  It  is  never 
hard  to  do  this  if  the  scaffold  has  been  correctly  de- 
signed and  constructed,  because  the  putlog  holes 
will  then  be  opposite  the  poles,  in  all  cases. 


SPRING  STAY  BRACES 


77 


Spring  braces  are  effective,  and  they  rarely  fail 
when  correctly  put  in.  The  brick  that  holds  the  com- 
ponent boards  of  the  brace  apart  should  be  set  as  near 
to  the  wall  as  is  consistent  with  bringing  the  outer  ends 
of  the  brace  together,  because  the  grip  of  the  brace  upon 
the  putlog  hole  is  greater,  the  nearer  the  wall  the  ful- 
crum brick  is  set.  Care  must  be  taken,  however,  to 
keep  this  brick  far  enough  from  the  wall  to  prevent 
overstraining  the  boards  composing  the  brace,  because 


FIG.  26.     AN  EXCELLENT  EXAMPLE  OF  SPRING  STAYING. 


78  BRICKLAYERS'  POLE  SCAFFOLD 

if  either  of  them  should  fracture,  the  efficacy  of  the 
brace  would  be  destroyed  at  once.  In  nailing  the 
outer  ends  of  a  spring  stay  to  the  ledger,  care  should 
be  taken  to  use  a  sufficient  number  of  nails  of  first-class 
quality,  and  to  have  them  large  enough  to  insure  the 
holding  of  the  brace  to  the  ledger. 

When  reliance  is  placed  wholly  upon  spring  braces 
for  maintaining  a  scaffold  at  a  proper  distance  from  the 
wall,  it  should  be  remembered  that  braces  of  this  kind 
give  little  or  no  lengthwise  stiffness  to  the  scaffold,  and 
separate  provision  should  therefore  be  made  for  insur- 
ing stability  in  that  direction. 

In  applying  spring  braces,  it  is  best  and  safest  to 
set  one  of  them  in  every  putlog  hole,  as  illustrated  in 
Fig.  26.  Many  builders  consider  it  sufficient,  however, 
to  set  them  in  the  holes  that  stand  opposite  the  even 
ledgers, — that  is,  in  the  holes  that  are  opposite  the 
second  ledger  of  the  scaffold,  and  opposite  the  fourth, 
sixth,  and  so  .on,  counting  upward  from  the  ground. 
The  omission  of  the  braces  from  every  other  row  of  holes, 
in  this  way,  may  or  may  not  be  justifiable,  according 
to  the  nature  of  the  scaffold  in  other  respects.  If  it 
is  low  and  lightly  loaded,  and  has  stout  and  sound  poles, 
the  omission  of  the  spring  braces  at  every  alternate 
ledger  may  be  defensible;  but  it  is  preferable,  under 
all  circumstances,  to  stay  the  scaffold  at  every  putlog 
hole,  as  recommended  above.  Whichever  plan  is 
adopted,  a  stay  should  be  provided  for  every  putlog 
hole  in  the  horizontal  rows  in  which  these  stays  are 
used,  because  it  is  important  that  every  pole  should  be 
supported ;  and  the  stays  should  never  be  omitted,  under 
any  circumstances,  from  more  than  every  alternate 
horizontal  row  of  putlog  holes.  It  is  particularly  im- 


SPECIAL  PUTLOGS  79 

portant  to  stiffen  the  scaffold,  by  spring  stays  or  other- 
wise, at  or  near  the  points  where  its  poles  are  spliced; 
because  the  poles  are  always  weaker  at  those  points 
than  they  are  elsewhere. 

When  spring  stays  are  used  for  bracing  a  scaffold, 
it  often  happens  that  some  of  the  places  where  stays 
are  needed  come  opposite  window  openings  in  the  wall. 
In  cases  of  this  kind  the  required  support  should  be 
provided  by  the  use  of  ordinary  straight  braces,  passing 
through  the  windows  to  the  flooring  as  described  in 
paragraph  48,  or  by  similar  braces  securely  fastened 
to  the  window  frames,  in  case  the  flooring  has  not  been 
laid  to  a  height  sufficient  to  afford  suitable  anchorage. 

5.1.  Caution  in  the  Use  of  Special  Putlogs.  When 
the  platform  of  the  scaffold  is  supported  by  putlogs  of 
special  form  (such  as  those  described  in  paragraph  41), 
which  are  designed  for  avoiding  the  necessity  of 
leaving  openings  in  the  wall  by  the  omission  of  bricks, 
the  bracing  is  often  glaringly  inadequate.  Spring 
stays  cannot  be  used  in  such  cases,  and  there  may 
be  but  few  window  openings.  It  is  all  too  common, 
under  these  circumstances,  to  merely  leave  some  of  the 
special  putlogs  in  position  as  the  scaffold  goes  up,  and 
to  rely  upon  them,  wholly,  for  obtaining  the  desired 
rigidity.  This  is  decidedly  inadvisable,  because  the 
holding  power  of  these  putlogs,  at  the  wall,  depends 
altogether  upon  the  way  in  which  the  workmen  lay 
the  bricks  and  mortar  around  them;  and  as  the  brick- 
layer often  gives  no  special  thought  to  the  holding 
power  that  the  putlog  is  to  have  in  its  subsequent 
capacity  as  a  brace,  he  is  likely  to  leave  its  inner  end  as 
free  as  possible,  to  facilitate  the  removal  of  the  putlog 
when  the  platform  is  raised,  or  when  the  scaffold  itself 


80  BRICKLAYERS'  POLE  SCAFFOLD 

is  taken  down.  Furthermore,  the  holding  power  of 
these  special  putlogs  is  zero  after  the  weight  of  the 
platform  has  been  removed  from  them,  unless  they  are 
nailed  to  the  ledgers ;  and  as  nailing  damages  the  putlog, 
it  is  apt  to  be  done  inadequately.  As  a  matter  of  fact, 
the  nailing  is  often  neglected  altogether,  and  where 
these  special  putlogs  are  used  it  is  not  uncommon  to 
find  that  only  a  few  of  them  are  nailed  either  to  the 
ledgers  or  to  the  poles.  A  scaffold  of  this  kind  some- 
times appears  to  be  properly  braced,  at  first  glance, 
although  it  may  become  evident,  upon  shaking  one  or 
two  of  the  poles,  that  most  of  the  putlogs  are  entirely 
free  from  the  poles  and  the  ledgers,  and  are  totally 
useless  as  braces.  It  is  clear,  therefore,  that  when 
putlogs  of  special  form  are  used,  the  foreman,  or  some 
other  person  skilled  in  scaffold  construction,  should  be 
specially  designated  as  a  supervisor  or  inspector  of  the 
bracing,  and  should  be-  held  personally  responsible  for 
the  safety  of  the  scaffold  in  this  respect. 

52.  Longitudinal  Bracing.  Adequate  provision  of 
some  sort  should  be  made  to  prevent  the  scaffold  from 
falling  in  a  direction  parallel  to  the  building,  as  sug- 
gested in  Fig.  25.  Too  little  attention  is  given  to  this 
point  in  American  practice,  and  it  is  often  hard  to 
understand  why  scaffolds  remain  standing,  instead  of 
collapsing  in  this  way.  For  the  necessary  resistance 
to  endwise  displacement,  builders  too  frequently  depend 
solely  upon  the  stiffness  of  the  connections  between 
the  ledgers  and  the  poles,  and  this  may  be  wholly  in- 
adequate if  the  load  upon  the  scaffold  is  more  than 
purely  nominal,  or  if  the  poles  are  not  straight  and 
truly  vertical.  To  strengthen  the  scaffold  in  the  direc- 
tion indicated,  a  positive  and  definite  provision  of 


LONGITUDINAL  BRACING 


81 


some  kind  should  be  made.  The  spring  stays  that  hold 
the  scaffold  to  the, wall  help  to  a  slight  extent,  but  they 
cannot  oppose  much  resistance  to  displacement  in  a 
direction  parallel  to  the  wall. 

When  the  scaffold  turns  a  corner,  a  considerable 
amount  of  stiffness  is  imparted  to  it  by  the  fact  that 
it  is  anchored  to  the  walls  in  two  different  directions, 
at  right  angles  to  each  other.  Window  bracing,  such 
as  is  described  in  paragraph  48,  may  be  fairly  effective 
for  stiffening  the  scaffold  in  a  direction  parallel  to  the 
wall,  provided  the  braces  that  run  to  the  windows  are 
inclined  to  the  wall  and  run  in  both  directions,  as  sug- 
gested in  the  closing  lines  of  that  paragraph.  It  is  far 


FIG.  27.     GUARD-RAIL  AND  FOOT-BOARD  ON  A  BRICKLAYERS' 
POLE  SCAFFOLD  IN  DRESDEN. 


82  BRICKLAYERS'   POLE  SCAFFOLD 

better,  however,  to  provide  diagonal  bracing  to  stiffen 
the  poles  and  prevent  collapse  by  the  method  under 
consideration.  It  will  not  be  necessary  to  consider 
the  details  of  this  form  of  bracing  in  the  present  para- 
graph, however,  because  the  subject  is  treated  fully  in 
paragraph  56,  to  which  the  reader  may  refer.  The 
principles  there  advocated,  in  connection  with  the  inde- 
pendent scaffold,  apply  with  but  little  modification  to 
the  bricklayers'  pole  scaffold  also. 

OTHER    SAFETY    MEASURES 

53.  Guard-rails,  Foot-boards,  etc.  These  im- 
portant features  receive  special  consideration  in  Section 
VII  (page  130),  to  which  reference  should  be  made. 
Fig.  27  shows  the  platform  of  a  bricklayers'  pole  scaf- 
fold in  Dresden,  Germany,  and  attention  is  particu- 
larly invited  to  the  foot -board  at  the  edge  of  the  plat- 
form, and  to  the  hand-rail  that  is  provided  at  a  proper 
height.  This  scaffold,  which  was  used  for  laying  the 
brick  wall  that  is  seen  on  the  right,  was  built  for  utility 
rather  than  for  beauty ;  but  it  was  well  designed,  and  it 
afforded  effective  protection  for  the  workmen. 


IV.     INDEPENDENT  POLE  SCAFFOLD:  AMERICAN 

PRACTICE. 

54.     Characteristics  of  the  Independent  Scaffold. 

The  independent  pole  scaffold  is  closely  similar  to  the 
bricklayers'  pole  scaffold,  the  essential  and  most  obvious 
point  of  difference  between  the  two,  as  the  names  are 
used  in  this  treatise,  being,  as  already  explained  in 
paragraph  7,  that  the  bricklayers'  pole  scaffold  is 
partly  supported  by  the  wall  beside  which  it  stands, 
while  the  independent  pole  scaffold  does  not  rest  upon 
the  wall  at  all,  but  is  supported  by  two  rows  of  poles  or 
uprights,  one  of  which  is  set  near  the  wall,  while  the 
other  stands  far  enough  away  from  it  to  allow  a  proper 
space  for  the  platform. 

The  independent  pole  scaffold  is  also  called  the 
' 'masons'  scaffold",  because  it  has  long  been  used  in 
the  erection  of  stone  buildings,  where  it  would  not  be 
convenient  to  make  places  for  the  putlogs  by  omitting 
stones  from  the  walls.  The  name  "independent" 
that  is  adopted  in  this  book  is  greatly  to  be  preferred, 
however,  not  only  because  it  is  to  some  extent  descrip- 
tive of  the  scaffold,  but  also  because  the  scaffold  is  used 
for  a  great  variety  of  purposes  in  addition  to  mason 
work.  It  is  extensively  employed,  for  example,  in 
repairing  and  decorating,  and  in  many  other  kinds  of 
work  in  which  defacement  of  the  walls  must  be  avoided. 
It  is  also  growing  in  favor,  quite  rapidly,  for  use  in  the 
laying  of  brick. 


84  INDEPENDENT  POLE  SCAFFOLD 

When  it  is  to  be  used  for  heavy  work,  the  independ- 
ent pole  scaffold  is  built  more  substantially  than  the 
bricklayers'  pole  scaffold,  and  its  platform  is  usually 
wider.  Each  set  of  poles  has  its  own  ledgers,  and  the 
cross-pieces  or  "bearers"  that  support  the  platform 
(and  which  correspond  to  the  "putlogs"  of  the  brick- 
layers' scaffold)  rest  upon  the  inner  ledgers  exactly 
as  they  do  upon  the  outer  ones.  The  inner  row  of  poles 
is  placed  near  the  wall,  but  space  enough  must  be  left 
behind  it  to  permit  the  men  to  work  there  without 
inconvenience. 

55.  Comparison  with  the  Bricklayers'  Pole  Scaffold. 
Much  that  has  been  said  in  connection  with  the  brick- 
layers' scaffold  applies  to  the  independent  scaffold  also. 
Spruce  is  strongly  recommended  for  all  its  parts,  and 
the  material  should  be  first-class  in  all  respects, — 
sound,  straight-grained,  well -seasoned,  and  free  from 
knots  and  all  other  defects.  The  footing  of  the  poles 
should  be  prepared  with  even  greater  care  than  is 
needed  for  the  bricklayers'  scaffold  (compare  para- 
graph 24),  because  the  independent  scaffold  usually 
has  less  support  from  the  building,  in  the  way  of 
bracing,  and  it  is  correspondingly  more  important  to 
give  scrupulous  attention  to  its  foundations.  Inde- 
pendent scaffolds  are  often  erected  upon  sidewalk 
sheds,  and  in  such  a  case  the  poles  of  the  scaffold  should 
be  made  to  rest  solidly  upon  large  cross-beams,  and 
be  fastened  to  them  securely.  A  construction  of  this 
type  calls  for  special  strength,  solidity,  and  rigidity, 
in  the  sidewalk  shed. 

In  the  independent  scaffold  the  bearer-bars,  upon 
which  the  platforms  rest  (and  which  correspond  to  the 
putlogs  of  the  bricklayers'  scaffold),  consist  of  pieces 


COMPARISON  WITH  BRICKLAYERS'  SCAFFOLD  85 


FIG.  28.     AN  INDEPENDENT  POLE  SCAFFOLD  FOR  LIGHT  WORK. 

(This  engraving  gives  a  good  idea  of  the  method  of  construction.     The  scaffold  should 
have  guard-rails  and  foot-boards,  however.) 


86  INDEPENDENT  POLE  SCAFFOLD 

of  plank  set  upon  edge  and  nailed  securely  to  the  up- 
rights in  such  a  way  that  they  rest  upon  the  top  edges 
of  the  ledgers,  both  at  the  front  and  at  the  back  of  the 
scaffold.  If  the  scaffold  is  to  be  used  in  construction 
work,  the  bearers  should  be  made  of  plank  from  1  1/2  in. 
to  2  in.  thick  (preferably  2  in.),  and  every  bearer  should 
be  secured  to  two  poles, — one  at  the  front  of  the  scaf- 
fold and  one  at  the  back, — by  at  least  four  20-penny 
nails  at  each  end.  If  the  scaffold  is  to  be  used  for  wall 
decoration,  or  for  some  other  light  purpose,  it  may  not 
be  necessary  to  adopt  quite  so  heavy  a  type  of  construc- 
tion. In  fact,  the  uses  of  the  independent  pole  scaffold 
are  so  varied  that  it  is  impossible  to  give  for  its  parts 
any  one  set  of  dimensions  that  would  be  generally 
applicable.  A  useful  idea  of  the  requirements  of  sound 
and  safe  design  can  be  had,  however,  from  the  data 
given  in  paragraph  57,  below. 

Fig.  28  shows  a  light  independent  pole  scaffold 
that  was  erected  for  cleaning  and  painting  the  wall  of 
a  building.  The  general  nature  of  the  independent 
scaffold  is  shown  very  well  in  this  illustration,  but  the 
actual  construction  of  this  particular  scaffold  is  not 
ideal  in  every  respect, — notably  because  there  are  no 
guard-rails  and  no  foot -boards. 

56.  Bracing.  As  the  independent  pole  scaffold 
receives  comparatively  little  support  from  the  building 
beside  which  it  stands,  it  is  highly  important  to 
strengthen  it  and  stiffen  it  very  thoroughly  by  system- 
atic and  careful  bracing. 

The  inner  and  outer  poles  should  be  connected 
by  diagonal  braces,  making  an  angle  of  about  45  de- 
grees with  the  ground.  (For  detailed  information  see 
paragraph  57.)  For  light  work  it  may  not  be  neces- 


BRACING  87 

sary  to  unite  every  pair  of  poles  in  this  way,  though  it  is 
always  best  to  do  so.  In  the  scaffold  shown  in  Fig.  28 
cross  bracing  of  this  kind  is  provided,  as  will  be  seen, 
for  every  alternate  pair  of  poles,  the  intermediate  pairs 
of  poles  being  unbraced. 

To  stiffen  the  scaffold  and  prevent  it  from  collap- 
sing in  a  direction  parallel  to  the  face  of  the  building  in 
the  way  suggested  in  Fig.  25,  diagonal  bracing,  making 
an  angle  of  about  45°  with  the  ground,  should  be  run 
from  pole  to  pole,  parallel  to  the  wall,  and  be  securely 
fastened  to  the  poles  by  a  sufficient  number  of  stout 
nails,  of  the  quality  indicated  in  paragraph  79.  Partic- 
ular attention  should  be  given  to  this  longitudinal 
bracing,  because  American  practice  is  distinctly  poor 
in  this  respect,  and  it  is  hoped  that  a  marked  and 
universal  improvement  may  soon  be  made. 

Longitudinal  braces  may  extend  merely  from  pole 
to  pole,  or  they  may  be  run  up  across  the  whole  face 
of  the  scaffold,  being  lengthened,  wherever  necessary, 
by  the  addition  of  more  pieces  running  in  the  same 
general  direction.  Numerous  examples  of  each  of  these 
methods  are  to  be  seen  in  the  illustrations  in  this  book. 
(See,  for  instance,  Figs.  3,  7,  32,  51,  and  63,  among 
others.)  Fig.  28  is  an  example  of  a  scaffold  braced  by 
one  "X"  extending  across  the  front  of  the  whole  struc- 
ture, and  another  one,  parallel  to  the  first,  extending 
entirely  across  the  rear  face.  It  is  not  customary  to  brace 
the  inner  poles  in  this  way,  in  guarding  against  displace- 
ment in  a  direction  parallel  to  the  face  of  the  wall ;  for 
although  this  adds  stiffness  to  the  structure,  the  bracing 
of  the  outer  row,  if  it  is  effectively  done,  is  usually 
sufficient  to  strengthen  the  whole  in  a  satisfactory 
manner. 


88 


INDEPENDENT  POLE  SCAFFOLD 


FIG.  29.     A  SCAFFOLD  STIFFENED  BY  NUMEROUS  SHORT  BRACES. 

(Note,  also,  the  guard-rails  and  foot-boards.) 

When  the  longitudinal  bracing  consists  of  com- 
paratively short  pieces  of  material  extending  merely 
from  pole  to  pole,  it  should  be  run  up  the  poles  like  a 
coarse  lattice-work,  so  as  to  tie  them  securely  from  top 
to  bottom.  It  is  not  always  necessary  to  provide  such  a 
lattice-work  between  every  pair  of  poles,  although  the 
structure  is  far  safer  if  this  is  done.  In  scaffolds  of 
moderate  height,  that  are  not  heavily  loaded,  sufficient 
stiffness  can  often  be  insured  by  erecting  a  lattice  of 
the  kind  described  at  every  other  bay, — that  is,  by 
uniting  the  first  pole  to  the  second  one,  the  third  to  the 
fourth,  the  fifth  to  the  sixth,  and  so  on. 

Fig.  29  shows  a  well-constructed  scaffold  that  was 
used  on  a  stone  building  in  Leipzig.  Doubled  poles  were 
adopted  for  the  uprights,  and  the  longitudinal  rigidity 


BRACING 


89 


FIG.  30.     A  WELL-BRACED  AMERICAN  SCAFFOLD. 

was  secured,  not  by  running  long  braces  across  the 
entire  face  of  the  scaffold,  but  by  uniting  every  pole 
with  each  of  its  neighbors  by  means  of  three  pairs  of 
shorter  braces.  The  guard-rails  and  foot-boards  of  this 
scaffold  should  also  be  noted,  as  they  were  installed 
in  a  highly  creditable  and  workmanlike  manner,  and 
might  well  serve  as  models  for  American  constructors. 
Fig.  30  shows  a  well-braced  independent  scaffold 
that  was  used  in  the  erection  of  a  brick  building  in 
Massachusetts.  As  will  be  seen,  this  scaffold  is  stiffened 
by  long  longitudinal  braces,  each  running  across  several 
poles ;  and  in  this  respect  it  contrasts  with  the  method 
of  bracing  that  is  shown  in  Fig.  29.  Fig.  30  is  an  excel- 
lent example  of  bracing,  yet  the  bracing  shown  in  Fig. 
29  is  probably  more  effective,  because  in  that  con- 


90  INDEPENDENT  POLE  SCAFFOLD 

struction  every  bay  between  consecutive  poles  is  fully 
braced,  whereas  in  Fig.  30  some  of  the  poles  are  united 
by  only  a  single  pair  of  braces. 

In  any  case,  whether  the  bracing  has  the  form  of  an 
"X"  or  consists  of  lattice-work  extending  merely  from 
one  pole  to  the  next,  the  constituent  pieces  composing 
it  should  run  in  both  directions,  so  that  the  scaffold 
may  be  efficiently  braced  against  falling  either  way. 
When  long  poles  or  stringers  are  used  and  arranged  like 
an  "X",  they  should  be  securely  nailed  or  lashed  to 
every  pole  that  they  cross. 

57.  Design  for  an  Independent  Pole  Scaffold. 
The  design  shown  in  Fig.  3 1  will  be  found  to  be  service- 
able and  safe,  for  pole  scaffolds  not  exceeding  100  feet 
in  height,  when  used  in  construction  work,  with  ordi- 
nary loads.  It  is  based  upon  extensive  experience, 
and  the  proportions  that  are  indicated  have  been 
thoroughly  tried  out  in  practice,  and  found  to  be 
satisfactory  for  service  of  this  kind ;  but  if  the  scaffold 
is  to  support  loads  of  greater  weight  than  are  likely  to 
occur  in  ordinary  building  operations,  the  various  parts 
should  be  proportionately  strengthened.  The  work- 
manship should  be  of  the  best,  in  all  respects,  and  the 
scaffold  should  be  constructed,  throughout,  of  spruce 
or  of  long -leaf  southern  pine.  The  material  should  be 
carefully  selected,  and  every  part  of  it  should  be  sound, 
straight,  straight-grained,  free  from  knots  and  all  other 
imperfections,  and  thoroughly  seasoned. 

When  a  scaffold  is  unusually  high,  or  is  to  be 
heavily  loaded,  it  is  advisable  to  bolt  its  parts  together. 
Nails  are  used  almost  exclusively  in  American  practice, 
however,  and  for  that  reason  we  assume,  in  what  fol- 
lows, that  the  scaffold  is  nailed  and  not  bolted.  Nails 


DESIGN  FOR  AN  INDEPENDENT  SCAFFOLD  91 

are  quite  satisfactory  under  ordinary  conditions,  but  it 
is  highly  important  to  use  them  in  sufficient  numbers, 
to  have  them  of  the  right  size,  and  to  see  that  they  are 
properly  distributed,  and  that  they  are  of  the  quality 
indicated  in  paragraph  79. 

The  poles,  A,  in  Fig.  31,  should  not  be  less  than  4 
inches  by  4  inches,  and  6  inches  by  6  inches  is  a  much 
better  size,  and  greatly  to  be  preferred.  Where  an 
upright  is  spliced,  as  at  B,  the  two  poles  that  are  to  be 
joined  should  be  sawed  off  truly  square,  and  the  upper 
one  should  be  set  upon  the  lower  one  so  that  their 
ends  will  match  accurately.  Cover-strips,  not  less 
than  36  inches  long  and  11/4  inches  thick,  and  equal 
in  width  to  the  respective  sides  of  the  poles  to  which 
they  are  applied,  should  be  nailed  to  the  upright  at  each 
splice,  on  two  sides  of  it  that  are  at  right  angles  to  each 
other.  Care  should  be  taken  to  see  that  the  middle 
point  of  each  strip  comes  opposite  the  splice  in  the 
upright,  and  each  strip  should  be  securely  nailed  to  the 
upright  with  not  less  than  ten  well-distributed  2Openny 
nails,  five  of  which  should  be  above  the  splice,  and  five 
below  it.  The  uprights  should  be  truly  vertical,  and 
great  care  should  be  taken  to  have  their  foundations 
secure  and  safe  in  every  respect.  (See  paragraphs  24, 
25,  and  55.)  The  splices  of  successive  poles  should  not 
come  opposite  one  another,  if  this  can  be  conveniently 
avoided. 

The  spacing  of  the  poles  will  depend,  to  a  consider- 
able extent,  upon  the  load  that  is  to  be  borne.  They 
should  not  be  set  more  than  10  feet  apart  (measuring 
from  center  to  center),  in  a  direction  parallel  to  the 
face  of  the  wall.  This  is  ordinarily  regarded  as  good 
practice,  when  the  other  parts  of  the  scaffold  have  the 


92 


INDEPENDENT  POLE  SCAFFOLD 

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DESIGN  FOR  AN  INDEPENDENT  SCAFFOLD  93 

sizes  suggested  in  this  section;  but  the  uprights  should 
be  set  closer  than  this  if  the  load  is  likely  to  be  unusu- 
ally heavy,  and  it  is  sometimes  advisable  to  place  them 
as  close  as  5  feet  from  center  to  center. 

The  outer  row  of  poles  should  be  about  9  feet  from 
the  inner  row;  and  as  it  is  important  for  the  scaffold 
to  have  a  base  wide  enough  to  insure  stability,  this 
distance  should  not  be  reduced,  even  under  heavy 
loading ; — the  increased  strength  that  is  called  for  under 
these  circumstances  being  obtained  by  other  means. 

The  inner  row  of  poles  should  be  set  from  24  to  36 
inches  from  the  wall,  not  only  to  allow  for  irregularities 
in  the  wall  where  ornamental  or  other  projections  exist, 
but  also  to  give  the  workmen  a  freer  access  to  the  wall 
than  could  be  had  if  the  poles  were  practically  in  con- 
tact with  it. 

The  ledgers  or  "running  strips",  C,  should  be  at 
least  9  inches  by  1  1/4  inches,  and  should  be  nailed  to 
each  pole  with  at  least  five  20-penny  nails.  The  vertical 
height  from  the  top  of  one  ledger  to  the  top  of  the  next 
will  depend  somewhat  upon  the  nature  of  the  work, 
but  an  interval  of  from  eight  feet  to  nine  feet  is  most 
convenient  under  ordinary  circumstances.  Ledgers 
should  never  be  spliced  between  the  poles.  They 
should  always  be  long  enough  to  extend  from  pole  to 
pole,  with  an  overlap  of  at  least  a  foot  at  each  pole; 
and  in  nailing  a  ledger  to  the  pole,  care  should  be  taken 
to  keep  the  nails  well  away  from  the  top  edge  of  it,  lest 
the  load  upon  the  ledger  cause  it  to  split. 

The  bearers,  D  (also  called  "bearer-bars"  or  "cross- 
bars"), which  correspond  to  the  putlogs  of  the  brick- 
layers' pole  scaffold,  consist  of  planks  set  upon  edge. 
They  rest  upon  the  ledgers,  and  are  also  nailed  to  the 


94  INDEPENDENT  POLE  SCAFFOLD 

poles.  Bearers  should  not  be  less  than  two  inches 
thick  and  nine  inches  wide,  and  they  should  be  secured 
to  the  poles  by  not  less  than  five  20-penny  nails  at  each 
end.  On  the  side  of  the  scaffold  furthest  from  the  wall, 
the  bearers  usually  project  beyond  the  poles,  to  a 
distance  of  one  foot  or  more,  and  on  the  side  toward  the 
wall  they  are  usually  allowed  to  project  sufficiently  to 
come  almost  into  contact  with  the  wall. 

The  cross-braces,  shown  at  E  in  Fig  31,  should  be 
not  less  than  nine  inches  wide  and  one  and  one-fourth 
inches  thick.  They  should  be  arranged  as  shown,  and 
should  be  secured  to  the  poles  by  not  less  than  four 
20-penny  nails  at  each  end.  Every  pole  in  the  front 
row  should  be  connected  to  the  pole  opposite  to  it  in  the 
back  row  by  at  least  one  brace  of  this  kind  between 
every  pair  of  ledgers,  as  indicated  in  the  engraving. 
When  the  scaffold  is  to  be  used  for  very  heavy  work, 
it  may  be  advisable  to  have  these  cross-braces  run 
in  both  directions,  instead  of  only  in  a  single  direction ; 
but  for  ordinary  loads  the  bracing  here  shown  should  be 
adequate,  if  the  scaffold  is  designed  and  constructed 
in  other  respects  in  conformity  with  the  suggestions 
in  this  section.  The  use  of  double  braces,  running  both 
ways  like  the  two  branches  of  an  "X",  makes  it  some- 
what inconvenient  for  the  workmen  to  pass  from  one 
part  of  the  scaffold  to  another,  along  platforms  where 
this  double  bracing  occurs.  At  the  free  end  of  the 
scaffold,  however,  the  cross-bracing  should  run  in  both 
directions,  because  considerable  additional  strength 
is  secured  by  this  construction,  and  the  "X"  is  not  in  the 
way  of  the  workmen  at  the  end  of  the  platform. 

The  longitudinal  braces,  indicated  at  F  in  the  en- 
graving, are  highly  important,  and  careful  attention 


DESIGN  FOR  AN  INDEPENDENT  SCAFFOLD  95 

should  be  paid  to  what  has  been  said  with  regard  to 
them  in  paragraph  56.  These  braces  should  be  not  less 
than  11/4  inches  thick,  and  8  or  9  inches  wide.  They 
may  be  simply  run  from  one  pole  to  the  next,  in  accord- 
ance with  the  scheme  shown  in  Fig.  29,  or  they  may  be 
extended  across  the  entire  face  of  the  scaffold,  some- 
what as  suggested  in  Fig.  30.  If  the  method  shown  in 
Fig.  29  is  adopted,  there  is  but  little  further  explanation 
to  be  given,  except  to  caution  the  builder  that  the  nail- 
ing should  be  good,  and  the  nails  ample  in  size,  and  (as 
is  assumed  throughout  the  book)  of  the  quality  indi- 
cated in  paragraph  79.  If  the  method  of  arrangement 
shown  in  Fig.  30  is  adopted,  a  few  further  words  of 
counsel  should  be  given.  In  this  case  the  braces 
should  be  securely  nailed  to  every  pole  that  they  cross, 
with  at  least  five  20-penny  nails  to  the  pole.  The 
splicing  of  the  longitudinal  braces  between  poles  should 
be  avoided  so  far  as  possible,  and  when  it  becomes 
necessary  to  splice  them  in  that  way  the  two  ends 
should  overlap  by  at  least  four  feet,  and  should  be 
nailed  together  with  not  less  than  five  well-distributed 
2  0-penny  nails.  A  scaffold  that  is  properly  constructed, 
and  built  of  selected  materials  in  conformity  with  the 
suggestions  of  this  section,  should  not  need  more 
longitudinal  bracing  than  is  shown  in  Fig.  30.  That  is, 
when  the  poles  are  spaced  ten  feet  apart,  it  should  be 
sufficient  to  start  one  longitudinal  brace  at  the  foot 
of  every  second  pole,  extending  it  upward  at  an  angle 
of  about  45°  to  the  top  of  the  scaffold.  The  longitudi- 
nal braces  should  run  in  both  directions,  however,  as 
indicated  in  Fig.  30. 

On  the  outer  row  of  poles,  the  ledgers  may  be 
attached,  most  conveniently,  to  the  side  of  the  poles 


96  INDEPENDENT  POLE  SCAFFOLD 

that  is  nearest  to  the  wall,  and  the  longitudinal  bracing 
can  then  be  applied  on  the  side  that  is  away  from  the 
wall.  It  is  not  customary  to  run  longitudinal  braces 
along  the  inner  row  of  poles,  because  they  interfere  with 
the  work,  and  experience  shows  that  sufficient  stiffness 
may  be  had  from  those  on  the  face  of  the  scaffold. 

With  a  construction  such  as  has  been  recommended 
above,  a  platform  may  be  laid  on  any  set  of  bearer-bars, 
and  the  number  of  platforms  that  are  used  will  naturally 
depend  upon  the  nature  of  the  work  that  is  to  be  done. 
It  is  advisable  to  lay  an  extra  platform  immediately 
over  every  level  on  which  men  are  working,  to  protect 
them  from  the  fall  of  tools  or  materials  from  above. 
It  is  also  advisable  to  lay  a  platform  on  every  third  set 
of  bearer-bars,  in  all  cases,  in  order  to  lessen  the  seri- 
ousness of  accidents  that  may  occur  by  the  falling  of 
men  who  are  at  work  about  the  scaffold.  Every  plat- 
form should  be  made  of  two-inch  planks,  laid  tight 
together  so  that  nothing  can  fall  down  between  them, 
and  disposed  so  that  they  will  overlap  the  bearer-bars 
by  the  same  amount  at  each  end.  When  the  poles 
are  spaced,  parallel  to  the  wall,  at  a  distance  of  ten 
feet  from  center  to  center,  and  the  planks  that  are  used 
are  twelve  feet  long,  this  will  allow  each  plank  to  over- 
lap the  center  of  each  bearer-bar  by  one  foot,  so  that  the 
successive  courses  of  planks  will  overlap  each  other  by 
two  feet  at  each  bearer-bar.  This  should  be  sufficient 
to  insure  safety.  If  the  poles  are  spaced  closer  than 
ten  feet  from  center  to  center,  twelve-foot  planks  may 
also  be  used,  and  allowed  to  overlap  to  a  correspond- 
ingly greater  extent ;  but  in  this  case  special  care  should 
be  taken  to  see  that  no  plank  is  left  with  its  free  end 
extending  more  than  about  one  foot  beyond  a  bearer- 


DESIGN  FOR  AN  INDEPENDENT  SCAFFOLD  97 

bar  or  other  safe  and  solid  support.  This  is  to  avoid 
danger  from  the  tipping  of  the  plank,  in  case  a  workman 
should  happen  to  step  upon  the  end  of  it,  or  deposit 
material  upon  it. 

When  an  independent  pole  scaffold  is  designed  as 
suggested  in  this  section,  the  interval  between  the 
bearer-bars  is  so  great  that  it  is  impossible  for  the  men 
to  work  on  the  wall  from  the  level  of  one  of  them  up  to 
that  of  the  next  one  above,  while  standing  directly 
upon  one  of  the  permanent  platforms.  A  single  tier 
of  horses  is  therefore  used,  as  indicated  in  the  illustra- 
tion, to  enable  the  men  to  reach  the  upper  part  of  this 
interval.  For  counsel  with  regard  to  horses,  see  Section 
IX,  page  153. 

For  security  against  displacement  by  settling,  or 
by  storms,  a  scaffold  of  the  kind  here  described  should 
be  securely  attached  to  the  wall  of  the  building,  at  or 
near  the  top,  when  this  wall  is  already  standing.  If 
the  wall  is  not  yet  built,  some  other  means  of  insuring 
stability  should  be  provided.  It  commonly  happens 
that  the  scaffold  turns  one  or  more  corners,  and  in  such 
a  case  sufficient  security  may  be  afforded  by  the  shape 
of  the  scaffold  itself,  if  it  is  solidly  built  in  accordance 
with  the  suggestions  herein  made.  It  is  impossible  to 
discuss  every  condition  that  may  arise,  but  special 
attention  should  be  given  to  the  stability  of  the  scaf- 
fold as  a  whole,  and  effective  measures  of  some  kind 
should  be  taken  to  insure  that  stability,  so  that  the 
structure  cannot  fall  over  bodily. 

For  gaining  access  to  the  different  levels  of  the 
scaffold,  it  is  strongly  recommended  that  stairways 
be  built  within  the  framework,  these  stairways  being 
provided  with  substantial  hand-rails,  as  suggested  in 


98  INDEPENDENT  POLE  SCAFFOLD 

paragraph  78.  If  ladders  are  used,  the  recommenda- 
tions in  paragraph  76  should  be  carefully  observed. 
It  is  best  to  run  the  ladders  inside  the  framework  of  the 
scaffold,  and  the  openings  where  they  come  up  through 
the  flooring  should  be  guarded  by  rails  and  foot -boards. 
58.  Guard-rails,  Foot-boards,  etc.  At  every  work- 
ing platform  on  the  scaffold,  guard-rails  and  foot-boards 
should  be  provided,  in  accordance  with  the  recom- 
mendations made  in  Section  VII,  page  130.  Special 
attention  should  be  paid  to  these  features,  because 
American  practice  is  commonly  poor  in  this  respect,  and 
the  tendency  of  our  builders  is  to  omit  these  important 
safeguards  entirely,  or  to  treat  them  altogether  inade- 
quately. The  use  of  wire  netting  is  also  strongly  advised, 
for  it  is  far  more  practical  on  independent  scaffolds  than 
it  is  on  scaffolds  of  the  bricklayers'  type.  (Compare 
paragraph  130.) 


V.     LASHED  SCAFFOLDS. 

59.     Characteristics   of  the   Lashed  Scaffold.     In 

Great  Britain,  and  in  Europe  generally,  the  various 
parts  of  scaffolds  are  frequently  secured  in  place  by 
ropes,  chains,  or  flexible  metallic  cords;  and  as  it  is 
convenient  to  have  a  definite,  all-inclusive  name  for 
scaffolds  that  are  erected  in  this  way,  we  shall  call  them 
all  "lashed  scaffolds".  Scaffolds  of  this  kind  were 
extensively  used  in  the  United  States,  in  former  times, 
but  American  practice  has  tended  away  from  this 
method  of  construction,  and  lashed  scaffolds  are  now 
rarely  seen  in  this  country.  They  are  not  actually 
obsolete,  but  they  are  so  uncommon  that  many  of  our 
scaffold  builders  no  longer  know  how  to  apply  the  rope 
fastenings,  so  as  to  insure  safety. 

When  round  wood  of  large  size  is  used  in  the  con- 
struction of  the  scaffold  (see  paragraph  60) ,  it  is  almost 
necessary  to  lash,  clamp,  or  bolt  the  parts  together, 
because  nails  are  hardly  applicable  in  this  case;  and 
even  when  sawed  material  is  employed,  the  use  of  rope 
is  favored  by  some  authorities  on  the  ground  that  the 
material  is  serviceable  for  a  much  longer  time  if  it  is 
lashed  together,  than  it  is  when  nails  are  used.  The 
damage  to  the  wooden  parts,  from  the  use  of  nails,  is 
not  confined  to  the  holes  that  are  made  in  driving  the 
nails  when  the  scaffold  is  first  erected ; — it  arises  largely 
from  the  splitting  of  the  various  parts  when  the  scaffold 
is  taken  down,  after  it  has  served  its  purpose. 


100 


LASHED  SCAFFOLDS 


FIG.  32.     AN  ENGLISH  LASHED  SCAFFOLD. 

(Note  the  protective  platforms,  the  bracing,  and  the  treatment  of  the  ladders.) 


CHARACTERISTICS  101 

Some  authorities  believe  that  American  builders 
will  return  to  the  lashed  scaffold,  after  a  time,  in  con- 
sequence of  the  increasing  price  of  lumber;  but  others 
assert  that  this  is  not  probable,  or  that  at  all  events 
it  will  not  come  to  pass  for  many  years, — partly 
because  the  material  deteriorates  to  a  considerable 
extent  from  the  effects  of  the  sun  and  weather,  even 
when  nails  are  not  used,  and  partly  because  the  saving 
in  labor  that  results  from  the  use  of  nails  is  marked 
enough  to  counteract  a  considerable  further  advance 
in  the  cost  of  lumber.  For  the  proper  erection  of  a 
scaffold  that  is  lashed  with  rope,  the  full  time  of  two 
men  is  required,  with  occasional  help  from  a  third; 
whereas  by  using  n'ails  a  bricklayers'  pole  scaffold  can 
be  erected  by  one  man,  with  occasional  help  from  a 
second  one  in  getting  the  uprights  into  position  and  in 
some  few  other  operations. 

When  rope  is  used  for  securing  the  parts  of  a  scaf- 
fold, it  is  extremely  important  that  the  lashing  should 
be  done  by  a  person  skilled  in  this  particular  kind  of 
work.  If  fiber  rope  is  used,  it  should  be  manila 
(not  sisal),  and  it  should  be  first-class  in  quality.  If 
there  is  any  doubt  about  its  condition,  it  should  either 
be  rejected,  or  be  tested  to  see  that  it  has  the  proper 
strength.  Rope  should  never  be  used  after  it  has  be- 
come seriously  weakened  by  exposure  to  the  weather,  and 
all  condemned  rope  should  be  destroyed,  so  that  it  cannot 
possibly  be  used  again,  either  by  accident  or  by  design. 

The  rope  employed  in  lashing  ledger  poles  to  up- 
rights is  usually  about  5/8  of  an  inch  in  diameter,  or  a 
little  less.  In  New  York  City,  18 -thread  tarred  ratline 
(which  is  a  little  more  than  half  an  inch  in  diameter) 
is  usually  employed  for  this  purpose. 


102 


LASHED  SCAFFOLDS 


FIG.  33.     FIRST  STAGE  IN  LASHING  A  LEDGER  TO  A  POLE. 

60.  Use  of  Round  Wood.  In  Europe,  the  poles 
and  ledgers  of  scaffolds  are  usually  made  of  round  wood, 
consisting  of  straight  sticks  from  which  the  bark  has 
been  peeled,  but  which  are  otherwise  left  substantially 
as  they  grew.  Wood  of  this  nature  is  stronger  than 
sawed  material  of  the  same  size  and  quality,  because  in 
a  sawed  piece  the  grain  seldom  or  never  runs  exactly 
parallel  to  the  length  of  the  stick,  but  often  runs  some- 
what diagonally  or  obliquely  to  it,  in  places.  The 


USE  OF  ROUND  WOOD 


103 


FIG.  34.     REAR  VIEW  OF  FIG.  33,  AFTER  TIGHTENING  THE  KNOT. 

fibers  of  the  sawed  pieces  are  therefore  severed,  here  and 
there ;  whereas  by  making  use  of  selected  natural  sticks, 
material  can  be  had,  every  fiber  of  which  runs  without 
interruption  from  one  end  to  the  other. 

In  the  United  States  round  wood  is  seldom  used 
in  bricklayers'  or  independent  pole  scaffolds,  the 
ledgers,  putlogs,  and  uprights  being  composed,  almost 
invariably,  of  sawed  timber;  but  round  wood  is  used 
here  to  a  limited  extent  in  certain  other  forms  of 


104 


LASHED  SCAFFOLDS 


FIG.  35.     FIRST  STAGE  IN  SECURING  THE  LEDGER. 

scaffolds,  particularly  when  the  conditions  are  such 
that  it  is  desirable  to  exercise  extraordinary  care  to 
insure  an  unusually  large  factor  of  safety.  For  ex- 
ample, the  stringers  that  supported  the  overhead  plat- 
form of  the  decorators'  scaffold  in  the  Grand  Cen- 
tral Terminal,  New  York  City,  and  which  may  be  seen 
just  below  the  ceiling  in  the  photograph  that  consti- 
tutes the  frontispiece  of  this  book,  were  made  of  selected 
natural  wood,  round,  and  untouched  by  a  saw  except 
where  they  were  squared  up  at  the  ends. 


TYING  THE  KNOTS 


105 


FIG.  36.     FINISHED  KNOT  AS  SEEN  FROM  THE  FRONT. 

61.  Tying  the  Knots.  When  a  ledger  is  to  be 
erected,  the  ropes  that  are  to  be  used  for  the  purpose 
should  first  be  tied  to  the  uprights,  in  the  position  that 
they  are  to  have  when  the  task  is  completed.  Each 
rope  should  be  at  least  seven  or  eight  feet  long,  and  the 
knot  that  secures  it  to  the  upright  should  be  in  the 
middle  of  its  length. 

Fig.  33  shows  how  the  rope  should  be  arranged  up- 
on the  pole, — the  knot  or  hitch  being  left  loose,  in 


106 


LASHED  SCAFFOLDS 


FIG.  37.     FINISHED  KNOT  AS  SEEN  FROM  BEHIND. 

taking  this  photograph,  so  that  the  relations  between 
its  various  parts  may  be  clearly  seen.  The  appear- 
ance of  the  rope  when  it  is  viewed  from  the  back  of  the 
pole  at  this  stage  is  shown  in  Fig.  34,  except  that  the 
loops  or  turns  of  the  rope  have  now  been  pushed  to- 
gether, and  the  hitch  properly  tightened  up. 

The  ledger  pole  is  next  laid  against  the  upright, 
with  its  lower  side  just  on  a  level  with  the  upper  part 
of  the  rope  in  the  hitch.  Each  end  of  the  rope  is  then 


TYING  THE  KNOTS  107 

carried  up  around  the  ledger  pole,  then  back  around 
the  upright,  and  finally  forward  again  and  down  over 
the  front  of  the  ledger.  This  brings  the  knot  into  the 
condition  shown  in  Fig.  35.  The  two  ends,  seen  de- 
pending in  this  illustration,  are  then  crossed  in  front 
of  the  ledger,  and  passed  under  it  and  up  behind  it, 
after  which  they  are  tied  in  a  square  knot,  over  the 
ledger  and  in  front  of  the  upright.  Fig.  36  shows  the 
completed  knot  as  seen  from  the  front  side,  and  Fig.  3  7 
shows  how  it  appears  from  behind. 

A  knot  tied  as  here  described  will  hold  the  ledger 
to  the  upright  under  the  heaviest  loads  that  the  rope 
can  bear,  and  it  should  never  slip  if  the  work  has  been 
carefully  done.  Attention  is  particularly  called  to 
the  way  in  which  the  ropes  lie  over  one  another,  beneath 
the  ledger  in  Fig.  36,  because  this  arrangement  causes 
the  parts  of  the  rope  to  bind  against  themselves  and 
against  the  pole,  in  such  a  way  that  they  become  tighter 
and  hold  more  securely  as  the  load  increases. 

In  fastening  a  ledger  in  this  way,  all  parts  of  the 
rope  should  be  drawn  as  tight  as  possible ;  and  in  tying 
the  final  knot,  special  care  should  be  taken  to  see  that 
it  is  a  true  square  knot,  instead  of  being  what  is  known 
among  sailors  as  a  "granny  knot". 

When  two  ledger  poles  come  together  at  one  up- 
right, the  knot  is  to  be  tied  precisely  as  described  above, 
except  that  the  two  ledger  poles  are  to  be  laid  one  over 
the  other,  and  the  rope  is  to  be  passed  around  them 
as  though  they  constituted  one  piece. 

62.  Splicing  the  Uprights.  When  rope  is  used  for 
fastening  the  parts  of  a  scaffold  together,  and  the  up- 
rights are  single  (instead  of  being  doubled  as  they  are  in 
the  high  scaffold  shown  in  Fig.  32),  it  is  customary  to 


108 


LASHED  SCAFFOLDS 


FIG.  38.     ILLUSTRATING  THE  LASHING  OF  THE  POLES. 

splice  the  uprights — not  by  placing  each  pole  squarely 
upon  the  top  of  the  one  immediately  below,  as  in  this 
country, — but  by  making  the  successive  uprights  over- 
lap by  from  six  to  ten  feet,  and  lashing  them  together 
with  rope.  A  stout  block  of  wood  should  be  nailed  to 
the  lower  pole,  to  assist  in  the  support  of  the  upper  one. 
In  fastening  two  overlapping  poles  together  with 
rope,  it  is  customary  to  lash  them  in  two  places,  one 
near  the  top  of  the  lower  pole  and  the  other  near  the 
bottom  of  the  upper  pole.  The  poles  that  are  employed 


SPLICING  THE  UPRIGHTS  109 

for  the  uprights  of  lashed  scaffolds  are  usually  about 
30  feet  long;  whereas  in  the  scaffolds  that  are  con- 
structed of  sawed  material,  in  this  country,  the  individ- 
ual poles  are  seldom  much  more  than  20  feet  long. 

In  lashing  a  pair  of  poles  together,  one  end  of  the 
rope  is  passed  around  the  two,  near  the  upper  end  of  the 
splice,  and  allowed  to  hang  down  in  a  nearly  vertical 
position  for  perhaps  four  or  five  feet.  It  should  not  be 
allowed  to  lie  entirely  within  the  angle  between  the  two 
poles,  but  should  be  kept  out  of  this  depression,  so 
that  the  next  operation  will  bind  it  down  to  the  poles 
as  effectively  as  possible. 

The  long  end  of  the  rope  is  now  wound  around  the 
poles  as  tightly  as  possible,  so  that  each  turn  of  the  rope 
bears  closely  against  the  preceding  one,  as  indicated  in 
Fig.  38.  When  the  lashing  has  attained  a  total  length 
of  18  inches  or  more,  according  to  the  load  that  is  to  be 
supported,  the  two  ends  of  the  rope  are  tied  together, 
as  firmly  as  possible,  by  a  square  knot.  The  operation 
just  described  is  then  repeated  with  another  piece  of 
rope  near  the  remaining  free  end  of  the  splice,  the  final 
appearance  being  indicated  in  Fig.  39. 

When  two  sets  of  poles,  lashed  together,  are  used 
for  the  uprights  for  the  purpose  of  securing  greater 
strength  and  stiffness,  the  splices  in  each  set  are  made 
to  come  as  nearly  as  possible  opposite  to  the  middle 
portions  of  the  poles  of  the  other  set.  In  extending 
the  poles  of  uprights  that  are  doubled  in  this  way,  each 
pole  is  made  to  rest  squarely  upon  the  end  of  the  one 
next  below,  and  at  every  splice  the  upper  and  lower 
poles  that  there  come  together  are  each  bound  to  the 
adjoining  pole  by  a  lashing  similar  to  that  shown  in 
Fig.  38.  (We  are  here  assuming  that  the  fastening  is 


110 


LASHED  SCAFFOLDS 


FIG.  39.     SHOWING  A  PAIR  OF  POLES  LASHED  TOGETHER 
IN  Two  PLACES. 

(A  block  should  be  nailed  to  the  lower  pole,  immediately  below  the  end  of  the  upper  one, 
to  make  the  support  more  effective.) 


SPLICING  THE  UPRIGHTS 


111 


FIG.  40.     DETAIL  VIEW  OF  A  Swiss  SCAFFOLD,  ILLUSTRATING  THE 
TREATMENT  OF  THE  POLES. 

effected  by  ropes.  For  data  respecting  the  use  of 
chains,  wire  cords,  clamps,  and  cramp-irons,  see  the 
three  following  paragraphs.)  Fig.  40,  which  is  a  detail 
view  of  a  scaffold  in  Zurich,  Switzerland,  illustrates 
this  construction  fairly  well.  Each  upright  here  con- 
sisted, at  its  lower  end,  of  three  poles,  united  by  wire 
cords  and  also  by  cramp-irons.  At  higher  elevations 
the  number  of  poles  to  an  upright  was  reduced  to  two, 


112 


LASHED  SCAFFOLDS 


and  at  the  top  a  single  pole  was  used.  It  can  be  seen, 
in  a  number  of  places,  that  the  ledger  poles  were  not 
merely  lashed  to  the  uprights,  but  that  a  more  effective 
support  was  provided  by  cutting  one  of  the  constitu- 
ents of  each  upright  to  lengths  equal  to  the  vertical 
distance  from  one  ledger  to  the  next.  Each  ledger 
rested  upon  the  end  of  one  of  these  short  poles,  and 
supported,  in  its  turn,  the  pole  next  above.  (This 
scaffold  is  far  from  being  a  model  one  in  other  respects, 
for  it  had  neither  hand-rails  nor  foot -boards.  More- 
over, the  diagonal  bracing  was  not  fastened  to  the 


FIG.  41.     ILLUSTRATING  THE  PROPER  FINISH  OF  THE  ENDS  OF 
WIRE  CORD  LASHINGS. 

uprights  with  a  degree  of  security  that  an  American 
engineer  would  deem  to  be  sufficient.) 

63.  Use  of  Wire  Cords  for  Lashing.  Flexible  wire 
cords  are  used  to  a  considerable  extent  for  lashing  the 
parts  of  scaffolds  together.  The  cords  that  are  used  are 
about  1/4  in.  in  diameter,  as  a  rule,  and  they  are  made 
long  enough  to  wrap  quite  a  number  of  times  around 
the  timbers  that  are  to  be  united,  so  as  to  insure 
strength.  Each  cord  should  be  provided  at  one  end 
with  a  thimble -like  cap  for  receiving  the  wires  and 
keeping  the  end  of  the  cord  in  good  condition,  and  at 
the  other  end  it  should  be  provided  with  an  eye,  which 


USE  OF  WIRE  CORDS 


113 


FIG.  42.     SCAFFOLD  POLES  UNITED  BY  WIRE  CORDS  AND  A  CHAIN. 

should  be  spliced  into  the  cord  in  a  thoroughly  work- 
manlike manner.  When  uprights  or  other  parts  have 
been  lashed  together  with  a  cord  of  this  kind,  the 
thimbled  end  of  the  cord  is  passed  through  the  eye  at 
the  opposite  end,  and  secured  as  effectively  as  possible, 
by  winding  it  about  the  strands  that  have  already 
been  wrapped  around  the  poles.  A  fastening  of  this 
kind  is  quite  effective.  It  is  easily  applied,  and  it  is  not 
likely  to  fail  if  the  cords  are  renewed  from  time  to 
time,  when  their  strands  become  worn,  strained,  or 
broken,  in  sendee. 


114 


LASHED  SCAFFOLDS 


Fig.  41  illustrates  the  way  in  which  the  ends  of  a 
wire  cord  should  be  finished,  for  use  in  lashing  a  scaf- 
fold, and  Fig.  42,  which  is  taken  from  a  London  scaffold, 
shows  four  large  poles  (two  of  which  are  diagonal  braces) 
lashed  together  by  wire  cord.  Two  of  the  poles  are  also 
united  by  chains,  as  explained  in  the  next  paragraph. 

64.  Use  of  Chains.  Chains  are  also  used  for 
fastening  the  parts  of  heavy  scaffolds  together,  and 
very  effective  connections  can  be  made  in  this  way. 

In  using  lashings  of  any  kind  it  is  essential  to  draw 
them  as  tight  as  possible,  so  that  they  will  bind  the 
parts  together  firmly  and  solidly.  For  tightening 
chain  connections  the  device  shown  in  Figs.  42,  43,  and 
44  is  sometimes  used.  This  is  placed  against  the  pole 
or  ledger  as  shown  in  Fig.  42,  a  small  projection  from 
the  center  of  its  base  (not  visible  in  the  engravings) 
penetrating  the  pole  by  perhaps  3/8  of  an  inch,  and 
serving  to  prevent  the  device  from  shifting  its  position 


FIG.  43.     CHAIN-TIGHTENING 

DEVICE:  APPEARANCE   WHEN 

THE  CHAIN  is  SLACK. 


FIG.  44.     CHAIN-TIGHTENING 

DEVICE:  APPEARANCE  WHEN 

THE  CHAIN  is  TIGHT. 


CLAMPS  AND  CRAMP-IRONS  115 

when  it  is  once  firmly  in  place.  (The  movable  part  of  the 
device,  at  this  stage,  is  screwed  down  into  the  position 
shown  in  Fig.  43 .)  The  chain  is  then  drawn  around  the 
poles  as  tightly  as  possible,  and  hooked  over  two  of  the 
projecting  ears  that  are  shown  in  Figs.  43  and  44.  The 
central  nut  of  the  device  is  then  turned  to  the  left,  so  as  to 
carry  the  ears  away  from  the  pole,  as  suggested  in  Fig. 
44, — the  nut  being  capable  of  turning  freely  without  caus- 
ing the  ears  to  revolve  at  the  same  time.  By  this  means 
the  chain  can  be  drawn  tight  enough  to  cause  it  to  sink 
into  the  wood  of  the  poles  to  an  appreciable  extent. 

The  device  here  described  is  excellent  in  theory, 
but  it  is  usually  made  of  cast  iron,  and  the  ears  some- 
times break  off  under  the  stress  that  is  thrown  upon 
them.  We  therefore  do  not  recommend  it  unless  it 
is  made  of  safer  material,  and  even  then  we  prefer 
to  secure  the  chain  in  some  other  way,  unless  the  loca- 
tion of  the  connection  is  such  that  no  great  harm 
would  be  likely  to  result  from  its  failure.  Moreover, 
we  consider  chains  to  be  distinctly  inferior,  in  any 
event,  to  high-grade  wire  rope  or  cord. 

65.  Use  of  Clamps  and  Cramp-irons.  Clamps  of 
many  kinds  are  used,  particularly  in  Europe,  for  support- 
ing ledgers  and  securing  them  to  the  uprights.  One  of 
the  forms  that  are  adapted  to  American  practice,  and 
used  here  to  some  extent,  is  shown  on  page  54.  Most  of 
the  clamps  that  have  been  devised  are  intended  for  use 
in  connection  with  ledgers  of  round  wood,  however,  and 
as  such  ledgers  are  not  commonly  employed  in  the 
United  States,  and  are  not  likely  to  come  into  general 
use  in  the  near  future,  it  does  not  appear  to  be  necessary 
to  discuss  the  various  special  clamps  that  are  made  for 
supporting  them. 


116  LASHED  SCAFFOLDS 

Cramp-irons  or  "dogs",  of  the  form  shown  in 
Fig.  45,  are  extensively  used  in  scaffold  construction 
throughout  Europe,  and  they  are  seen  to  some  slight 
extent  in  this  country  also.  The  iron  that  is  repre- 
sented in  Fig.  45,  is  about  10  in.  long,  and  the  body 
of  it  is  7/8  in.  wide  and  5/16  in.  thick.  The  points  are 
forged  up  at  the  ends,  and  are  about  2  5/8  in.  long.  In 
a  new  iron  the  points  stand  nearly  at  right  angles  to 
the  body,  but  they  should  flare  outward  to  a  slight 
extent,  so  that  when  they  are  driven  in,  they  will 
draw  the  parts  that  they  enter  more  closely  together. 
The  illustration  was  made  from  an  old  specimen  that 


FIG.  45.     A  CRAMP-IRON. 

(Overstrained  by  use,  and  cracked  where  indicated  by  the  arrows.) 

had  seen  considerable  service.  The  points,  as  will  be 
seen,  had  become  bent  outward  to  a  considerable 
extent,  and  a  well-defined  crack  had  also  developed, 
at  each  end,  in  the  angles  where  the  points  join  the 
body.  If  cramp-irons  of  this  kind  are  employed,  they 
should  be  carefully  forged  up  from  first-class  material, 
possessing  a  high  degree  of  ductility. 

A  good  idea  of  the  way  in  which  these  irons  are  used 
can  be  had  from  the  accompanying  illustrations,  which 
show  them  in  a  number  of  different  applications.  They 


CLAMPS  AND  CRAMP-IRONS 


117 


FIG.  46.     CRAMP-IRONS  SUPPORTING  A  HORIZONTAL  BRACE. 

are  used  not  only  for  uniting  the  various  parts  of  the 
scaffold,  but  also  to  steady  ladders,  and  to  afford  points 
of  support  for  pieces  under  which  cleats  or  blocks  would 
be  placed  in  American  practice.  With  all  due  defer- 
ence to  the  opinions  of  European  engineers,  however, 
we  prefer,  in  most  cases,  a  more  positive  form  of  con- 
nection than  is  afforded  by  cramp-irons  of  this  nature. 

Fig.  46  shows  three  of  the  irons  in  use  for  securing  a 
horizontal  brace  to  a  ladder.  The  ladder  in  this  case 
was  made  stout  enough  to  serve  as  a  support  to  the 
scaffold.  (A  better  idea  of  the  general  nature  of  the  scaf- 


118 


LASHED  SCAFFOLDS 


fold  of  which  this  is  a  detail  can  be  had  from  Fig.  53, 
where  each  of  the  uprights  consists  of  a  similar  ladder.) 
The  method  here  shown  for  securing  the  brace  does  not 
commend  itself  to  American  safety  engineers,  unless  it 
is  supplemented  by  some  other  mode  of  attachment. 
It  will  be  seen  that  one  iron  is  driven  into  the  ladder  at 
both  ends,  below  the  horizontal  stringer,  to  serve  as  a 
point  of  support  for  it;  and  if  this  iron  should  fail,  the 
brace  would  be  likely  to  fall  by  revolving  in  the  direc- 
tion of  the  hands  of  a  clock,  and  thereby  tearing  itself 
loose  from  the  two  irons  that  support  it  from  above. 


FIG.  47.     CRAMP-IRONS  AS  APPLIED  AROUND  THE  FOOT  OF  A 
SCAFFOLD  UPRIGHT. 


GUARD-RAILS  119 

Fig.  47  shows  a  number  of  irons  applied  to  hold 
various  parts  of  a  scaffold  together,  around  the  base 
of  one  of  the  vertical  supports.  Although  the  photo- 
graph does  not  show  the  fact  as  clearly  as  could  be 
wished,  the  upright  was  composed  of  two  poles,  and 
the  two  uppermost  irons  on  the  front  of  the  scaffold  are 
driven  in  so  that  they  serve  to  hold  these  two  poles 
together. 

66.  Bracing.     The  principles  that  underlie  the 
bracing  of  lashed  scaffolds  are  in  no  way  different  from 
those  that  relate  to  the  independent  pole  scaffold,  as 
described  in  paragraph  56.     The  differences  in  practice 
that  exist  relate  merely  to  the  methods  by  which  the 
braces  are  secured  to  the  other  parts  of  the  structure, 
and  these  have  been  described  in  the  last  few  paragraphs. 

67.  Guard-rails,  Foot-boards,  etc.     These  import- 
ant safety  features  are  considered  in  Section  VII,  page 
130,  to  which  reference  should  be  made. 


VI.  OTHER  FORMS  OF  POLE  SCAFFOLDS. 

68.  Pole  Scaffolds  with  Iron  Supports.  A  form 
of  scaffold  that  is  used  by  bricklayers  to  a  limited 
extent,  and  which  is  analogous  to  the  bricklayers'  pole 
scaffold  described  in  Section  III  (page  38),  is  shown  in 
Fig.  48.  In  this  construction  the  uprights  consist  of 
angle-irons  of  special  form,  one  of  which  is  shown  in  the 
upper  part  of  Fig.  49.  The  uprights  sometimes  rest 
upon  the  ground,  and  sometimes,  as  an  alternative 
construction,  they  are  supported  by  iron  brackets,  as 
indicated  in  Figs.  48  and  50.  Each  upright  that  rests 
upon  the  ground  is  provided  with  a  special  foot  like 


FIG.  48.     BRICKLAYERS'  SCAFFOLD  WITH  IRON  SUPPORTS. 


POLE  SCAFFOLDS  WITH   IRON  SUPPORTS 


121 


that  shown  in  Fig.  49,  consisting  of  a  circular  iron  plate 
about  18  inches  in  diameter,  which  is  dished  at  the 
edges  and  provided  with  gusset -like  ribs  or  braces. 

Fig.  50  gives  a  detailed  view  of  the  brackets  that 
are  used  on  this  scaffold,  when  it  is  not  convenient 
to  have  the  uprights  bear  directly  upon  the  ground. 
The  horizontal  arms  of  these  brackets  are  attached  to 
ears  that  are  built  into  the  wall,  and  the  brackets  are 
prevented  from  swinging  sidewise  by  stay-rods  extend- 
ing from  their  outer  extremities  to  other  ears  that 
are  also  built  into  the  wall,  and  provided  with  turn- 


FIG.  49.     FOOT  OF  IRON  POLE. 


122 


OTHER  FORMS  OF  POLE  SCAFFOLDS 


FIG.  50.     IRON  BRACKETS  FOR  BRICKLAYERS'  SCAFFOLD. 

buckles  by  which  they  can  be  tightened.  It  is  important 
to  have  the  stay-rods  as  nearly  horizontal  as  possible, 
instead  of  inclining  them  downward  as  shown  in  the 
engravings;  because  when  they  are  horizontal  they 
afford  additional  security  against  the  overturning  of  the 
brackets  by  the  weight  that  rests  upon  them,  whereas 
if  they  are  put  in  so  that  the  ears  to  which  they  are 
attached  are  nearly  on  a  level  with  the  feet  of  the  braces, 
they  afford  no  support  of  this  kind,  whatsoever.  The 
various  parts  of  the  scaffold  are  held  together  by  special 


LADDER  SCAFFOLDS  123 

clamps,  which  are  designed  for  the  purpose  and  fur- 
nished by  the  makers  of  the  scaffold. 

The  use  of  this  scaffold  is  quite  limited  in  the 
United  States,  although  in  a  slightly  different  form  it 
has  been  employed  in  England  for  a  number  of  years. 
When  the  structure  is  erected  by  the  use  of  brackets, 
its  safety  depends  altogether  upon  the  security  with 
which  the  ears  that  hold  the  brackets  and  their  stay- 
rods  are  built  into  the  wall.  The  most  scrupulous 
attention  should  therefore  be  paid  to  this  point,  and 
special  care  should  also  be  taken  to  prevent  the  work- 
men from  loading  the  platform  with  any  considerable 
weight  of  material. 

69.  Ladder  Scaffolds.  In  many  parts  of  Europe 
a  convenient  and  useful  form  of  light  scaffolding  is 
extensively  used,  which  is  seldom  or  never  seen  in  the 
United  States.  We  refer  to  the  "ladder  scaffold", 
which  takes  its  name  from  the  fact  that  it  is  supported 
by  vertical  ladders  of  a  somewhat  special  form,  instead 
of  by  simple  poles.  The  ladders  are  set  upon  end,  and 
their  rungs  support  horizontal  planks  which  serve  as 
platforms.  The  side-bars  of  the  ladders  play  the  part 
of  the  poles  of  the  independent  scaffold,  and  the  rungs 
that  support  the  planks  play  the  part  of  bearer-bars 
or  putlogs.  The  construction  will  be  clearly  understood 
by  referring  to  Figs.  51  and  52,  which  show  two  slightly 
different  forms  of  the  ladder  scaffold. 

These  scaffolds  are  often  extended  to  great  heights, 
but  as  ordinarily  constructed  they  are  not  adapted  to 
heavy  work,  nor  to  the  support  of  materials.  They  are 
exceedingly  useful,  however,  for  light  work,  such  as 
cleaning  walls,  painting,  and  making  general  repairs; 
and  when  they  are  made  strongly  and  in  accordance 


124  OTHER  FORMS  OF  POLE  SCAFFOLDS 

with  special  designs,  and  are  erected  by  men  skilled  in  this 
kind  of  service,  they  are  used  in  construction  work  also. 

To  protect  the  workmen  from  falling,  ladder  scaf- 
folds should  be  provided  with  guard-rails  at  least  6  in. 
wide  and  1  in.  thick,  as  shown  in  the  illustrations. 
(The  man  directly  under  the  cross  in  Fig.  51,  for  ex- 
ample, is  leaning  upon  one  of  the  guard-rails.)  They 
are  rarely  fitted  with  foot -boards,  because  they  are  not 
supposed  to  be  used  for  the  support  of  materials;  but 
the  heavier  scaffolds  of  this  type  are  likely  to  have  tools 
and  a  certain  amount  of  materials  upon  their  plat- 
forms, and  in  such  cases  foot -boards  should  always 
be  provided. 

To  facilitate  passing  along  the  plank  platforms 
from  one  part  of  the  scaffold  to  another  at  the  same 
level,  rungs  are  often  omitted  from  the  ladder  at  inter- 
vals. An  example  of  this  is  shown  in  Fig.  52,  where 
spaces  for  the  passage  of  the  men  are  provided  by  omit- 
ting the  second  rung  above  each  line  of  planks.  The 
openings  thus  made  are  usually  about  36  in.  high  and 
perhaps  20  in.  wide. 

Ladder  scaffolds  should  be  securely  attached  to  the 
building  at  every  story,  either  by  braces  passing 
through  the  window  openings,  or  by  lashings  made  fast 
to  ears  or  eyes  that  are  secured  to  the  walls  in  some 
safe  manner;  and  the  height  from  one  such  brace  or 
lashing  to  the  next  should  never  exceed  20  feet.  The 
scaffold  should  also  be  effectively  stiffened  by  diagonal 
bracing,  similar  to  that  described  in  paragraph  56 
in  connection  with  the  independent  pole  scaffold  that 
is  used  in  the  United  States.  (See  Fig.  51.) 

The  German  regulations  that  apply  to  these  scaf- 
folds specify  that  the  ladders  must  not  rest  directly 


LADDER  SCAFFOLDS  125 

upon  the  ground  or  sidewalk,  but  require  that  every 
ladder  shall  stand  upon  pieces  of  plank  so  placed  that 
the  two  side-bars  will  bear  upon  them  equally,  and  with 
their  full  load.  It  is  further  specified  that  the  ladders 
shall  not  be  more  than  12  feet  apart,  and  that  any 
blocking-up  that  may  be  necessary  shall  be  effected 
only  by  the  use  of  broad  wooden  wedges, — the  use  of 


FIG.  51.     A  LADDER  SCAFFOLD,  FOR  LIGHT  WORK. 


126  OTHER  FORMS  OF  POLE  SCAFFOLDS 

stone  or  iron  for  this  purpose  being  expressly  forbidden, 
— and  that  the  wedges  shall  be  effectively  fastened  in 
place. 

To  extend  the  ladders  in  a  vertical  direction,  the 
upper  ladder  is  spliced  to  the  one  below  by  overlapping 
the  two  and  connecting  them  by  hooks  if  the  scaffold 
is  a  light  one,  or  by  splice-plates  and  bolts  if  it  is  in- 
tended for  heavier  work.  Where  these  connections 
are  made,  the  ladders  have  iron  bolts  in  the  place  of 
rungs,  to  receive  the  hooks  or  splice-plates;  and  the 
German  regulations  specify  that  these  bolts  shall  not 
be  less  than  one  inch  in  diameter. 

The  workmen  should  not  climb  up  by  the  ladders 
that  serve  to  support  the  scaffold.  Access  to  the 
various  platforms  should  be  had  from  the  building 
itself,  or  by  the  use  of  ladders  of  the  ordinary  form, 
specially  provided  for  this  purpose.  Ladders  for  climb- 
ing should  be  located  within  the  framework  of  the 
scaffold  whenever  possible,  so  that  the  workmen,  in 
using  them,  may  have  the  protection  of  the  guard-rails 
at  the  various  platform  levels.  (An  external  ladder, 
provided  for  the  ascent  of  the  workmen,  is  shown  at 
A  in  Fig.  51.) 

The  platform  planks  should  be  at  least  11/2  inches 
thick,  and  when  a  platform  consists  of  two  courses  of 
plank  laid  side  by  side,  the  two  courses  should  be  con- 
nected, at  the  middle  of  each  span,  by  a  clamp  or 
stirrup  that  embraces  both  planks  and  holds  them 
securely  together.  Several  of  these  stirrups  can  be 
seen,  though  somewhat  imperfectly,  in  Fig.  52. 

The  most  distinctive  thing  about  the  ladder  scaf- 
fold is  the  fact  that  it  is  built  so  that  it  can  be  erected 
and  taken  down  again,  without  damage,  and  can  there- 


LADDER  SCAFFOLDS 


127 


fore  be  used  repeatedly.  The  entire  scaffold  is  made 
adjustable,  each  guard-rail  and  brace  being  provided 
with  a  series  of  holes  at  one  end  and  with  a  slot  at  the 
other,  so  that  it  can  be  bolted  to  the  ladders,  wherever 
these  may  stand. 

Scaffolds  of  this  type  are  owned  by  companies 
that  lease  them  to  the  users,  the  rental  covering  the 
work  of  erection  and  removal,  which  is  performed  by 


FIG.  52.     A  LADDER  SCAFFOLD,  DIFFERING  SLIGHTLY  IN 
DESIGN  FROM  FIG.  51. 


128 


OTHER  FORMS  OF  POLE  SCAFFOLDS 


the  owners.  They  are  extensively  used  in  Germany, 
Switzerland,  France,  and  Austria,  and  for  doing  light 
work  they  are  exceedingly  satisfactory,  and  they  are 
also  relatively  inexpensive,  because  there  is  no  destruc- 
tion of  material  in  using  them.  There  does  not  appear 
to  be  any  good  reason  why  they  should  not  be  widely 


FIG.  53.     A  SCAFFOLD  OF  THE  BRICKLAYERS'  POLE  TYPE,  BUT 
WITH  STOUT  LADDERS  FOR  UPRIGHTS. 

(From  the  new  German  Museum  Building,  Munich.) 


LADDER  SCAFFOLDS  129 

adopted  in  the  United  States  also,  and  we  are  of  the 
opinion  that  they  soon  will  be.  They  have  been  used 
in  Germany  for  more  than  25  years. 

Fig.  53  shows  a  special  form  of  ladder  scaffold 
that  is  used  in  Germany  for  construction  work.  It  is 
similar  in  its  general  design  to  the  American  brick- 
layers' pole  scaffold.  There  is  but  one  row  of  uprights, 
and  each  upright  is  a  ladder  of  extra-heavy  material. 
In  the  scaffold  from  which  this  photograph  was  taken 
there  was  no  diagonal  bracing.  The  working  platform, 
which  is  at  the  very  top  in  the  engraving,  was  inclosed, 
however,  by  an  effective  fence  composed  in  some  places 
of  three  boards  and  in  other  places  of  four,  in  addition 
to  the  foot -board.  It  will  be  noticed  that  the  support- 
ing ladders  lean  toward  the  building,  so  as  to  afford 
greater  security.  The  timbers  of  this  scaffold  were 
fastened  together  partly  by  cramp-irons  and  partly  by 
rope  lashings.  A  detailed  view  of  a  section  of  it,  in 
which  cramp-irons  were  used  without  any  lashing,  is 
given  in  Fig.  46. 


VII.     SPECIAL  SAFETY  FEATURES. 

70.  General  Considerations.  Thus  far  we  have 
treated  mainly  of  the  strength  and  stability  of  the 
scaffold.  In  the  present  section  we  shall  consider  cer- 
tain other  features  that  relate  to  safety  alone,  and  have 
little  or  no  relation  to  the  security  of  the  structure  itself. 
Prominent  among  these  are  guard-rails,  foot -boards, 
wire-net  screens  along  the  sides  of  the  working  plat- 
forms, and  special  protective  roofs,  or  coverings,  over 
passageways  and  workplaces  where  men  may  be  ex- 
posed to  danger  through  the  falling  of  materials  from 
the  scaffold  above.  Safeguards  of  this  nature  often 
receive  scant  attention  in  American  practice ;  but  they 
are  of  great  practical  value,  and  the  systematic  adoption 
of  them  would  materially  reduce  the  scaffold  accidents 
that  now  occur. 

The  particular  protective  features  that  are  men- 
tioned above  are  simple  and  inexpensive,  and  they 
should  be  applied  to  every  scaffold  to  which  they  can  be 
adapted.  (Compare  paragraph  89.)  Fig.  27  shows 
an  ordinary  bricklayers'  pole  scaffold  with  a  hand-rail 
and  foot -board  applied  to  it,  and  in  Fig.  29,  which 
shows  an  independent  scaffold  in  Leipzig,  Germany, 
the  hand-rails  and  foot -boards  can  also  be  seen. 

The  protective  features  that  we  have  mentioned 
above  are  particularly  important  in  connection  with 
the  suspended  scaffolds  that  are  now  so  widely  em- 
ployed by  bricklayers,  because  these  scaffolds  'are  used 


GUARD-RAILS  131 

at  great  heights,  so  that  a  workman  falling  from  one  of 
them  would  surely  be  killed,  and  the  fall  of  a  small  piece 
of  material  might  produce  serious  consequences  to  a 
person  below.  The  special  features  that  are  involved 
in  applying  hand-rails  and  foot -boards  to  suspended 
scaffolds  are  considered  in  paragraph  130. 

71.  Guard-rails.  To  protect  the  workmen  from 
falling  to  the  ground  in  case  they  should  trip  or  stum- 
ble, a  guard-rail  or  hand-rail  should  be  provided  along 
the  outer  edge  of  the  working  platform  at  a  height  of 
about  40  inches,  measuring  from  the  platform  to  the 
upper  edge  of  the  rail.  A  rail  of  this  kind  should  be 
strong  and  substantial,  and  it  should  be  made  of 
selected,  straight-grained  material,  free  from  knots. 
It  should  be  securely  nailed  to  the  poles,  preferably 
on  the  side  facing  the  platform,  because  a  falling  man 
is  safer  when  his  weight  tends  to  push  the  rail  against 
the  poles  than  he  is  when  reliance  must  be  placed  solely 
upon  the  holding  power  of  the  nails.  The  rail  may 
with  advantage  be  6  in.  wide  and  1  in.  thick,  though 
there  is  no  need  of  insisting  upon  these  exact  dimen- 
sions. The  main  points  are,  to  be  sure  that  the  rail 
is  strongly  secured  to  the  poles  in  every  case,  and  that 
it  is  able  to  resist,  without  the  slightest  uncertainty,  the 
shock  to  which  it  would  be  subjected  if  a  heavy  man 
should  fall  against  it  forcibly.  In  some  cases  it  is 
advisable  to  put  up  a  second  rail  at  about  half  the  height 
of  the  first  one,  to  give  additional  protection  against 
the  fall  of  workmen  or  of  materials.  Rope  is  some- 
times tied  from  pole  to  pole,  along  the  edge  of  a  scaf- 
fold, to  take  the  place  of  a  more  substantial  railing. 
It  is  distinctly  inferior,  however,  and  it  should  be  used 
only  when  a  proper  wooden  rail  is  not  available.  In 


132  SPECIAL  SAFETY  FEATURES 

erecting  a  bricklayers  "pole  scaffold,  some  builders  nail 
the  next  ledger  to  the  poles  at  the  time  the  platform 
is  laid,  so  that  it  can  serve  as  a  guard-rail.  This  is 
better  than  omitting  the  guard-rail  altogether,  but  it 
is  nevertheless  far  from  satisfactory,  because  the 
ledger  comes  so  high  that  there  is  plenty  of  room  for  a 
man  to  plunge  down  under  it,  if  he  should  trip.  It  is 
always  a  mistake  to  rely  upon  a  makeshift  substitute 
like  this.  It  is  very  little  trouble  to  erect  a  special 
guard-rail  that  will  be  really  effective,  and  this  should 
be  done  in  every  case,  at  the  proper  time.  A  guard- 
rail should  extend  across  the  platform  from  the  upright 
to  the  building,  wherever  there  is  a  free  end  to  the 
scaffold  platform.  This  point  is  often  neglected,  even 
when  the  railing  is  well  done  at  other  parts  of  the  scaf- 
fold. It  is  very  important,  however,  because  many 
men  are  killed  or  injured  by  falling  from  platforms 
at  the  end.  Where  the  scaffold  turns  a  corner,  one  of 
the  guard-rails  may  be  sprung  so  as  to  be  nailed  to  the 
outer  surface  of  the  corner  pole,  while  the  other  one 
is  nailed  to  the  inside  of  the  pole. 

Of  the  various  wroods  that  are  available  for  the 
construction  of  guard-rails,  spruce  is  doubtless  the  best. 

72.  Foot-boards.  To  prevent  materials  from 
falling  over  the  edge  of  the  platform  and  injuring  work- 
men or  other  persons  below,  a  foot-board  (or  "toe- 
board")  should  be  erected  along  the  outer  margin  of 
the  scaffold  platform,  resting  snugly  against  the  outer- 
most plank,  so  as  to  leave  no  space  at  this  point. 
The  foot -board  should  project  above  the  platform  by 
not  less  than  7  inches.  It  is  important  to  have  the 
foot-board  fit  against  the  platform  as  perfectly  as 
possible,  at  all  points,  and  care  should  be  taken  to  see 


FOOT-BOARDS 


133 


FIG.    54.     ALL   FOOT-BOARDS 
RESTING  ON  THE  PUTLOGS. 

(Tools  or  materials  can  fall  through,   as 
shown  by  the  arrow.) 


FIG.    55.     ALL   FOOT-BOARDS 
RESTING  ON  THE  PLATFORM. 

(Tools  or  materials  can  fall  through,  as. 
shown  by  the  arrow.) 


FIG.   56.     FOOT-BOARDS  RESTING  ALTERNATELY  ON  THE  PUT- 
LOGS AND  THE  PLATFORM  PLANKS. 

(All  joints  are  tight,  and  nothing  can  fall  through.) 


134  SPECIAL  SAFETY  FEATURES 

that  it  does  so.  If  the  boards  or  planks  that  constitute 
the  foot -board  rest  upon  edge  on  the  putlogs  or  bearer- 
bars,  and  overlap  each  other  as  shown  in  Fig.  54, 
every  other  length  of  the  foot -board  planks  will  stand 
off  slightly  from  the  platform  as  indicated  by  the  arrow. 
This  particular  difficulty  may  be  removed  by  making 
the  foot -board  rest  upon  the  planking  instead  of  upon 
the  putlogs,  as  shown  in  Fig.  55 ;  but  when  this  plan  is 
adopted  every  alternate  foot -board  will  stand  up  from 
the  platform,  leaving  a  space  equal  to  the  thickness 
of  a  plank,  between  the  lower  edge  of  the  foot-board 
and  the  upper  surface  of  the  platform.  These  objec- 
tionable features  may  both  be  avoided  by  letting  the 
foot -boards  rest  alternately  upon  the  putlogs  and  upon 
the  platform,  as  shown  in  Fig.  56.  Tight  joints  are 
easily  made  in  this  way,  and  the  only  objection  to  the 
method  is,  that  one  foot -board  will  stand  four  inches 
higher  (or  lower)  than  the  one  next  to  it,  if  all  are  of 
the  same  width,  and  the  platform  planks  are  two  inches 
thick.  This  is  of  no  particular  importance,  provided 
the  lower  one  stands  at  a  safe  height.  Moreover,  there 
is  no  good  reason  why  the  material  used  for  the  foot- 
boards should  be  of  a  uniform  width ;  and  if  two  widths 
are  used, — one  four  inches  greater  than  the  other, — 
the  foot-boards  can  be  erected  in  accordance  with  the 
scheme  shown  in  Fig.  56,  and  still  be  in  line  along  their 
upper  edges. 

The  foot -boards  may  be  secured  either  to  the  plank- 
ing or  to  the  poles,  but  it  is  far  better  to  secure  them  to 
the  poles.  They  should  also  overlap  each  other  at  the 
poles,  and  never  at  points  between  the  poles,  where  they 
are  not  supported.  Where  two  foot -boards  come 
together  at  a  corner,  one  of  them  should  project  beyond 


WIRE  NETTING  135 

the  corner,  and  the  second  board  should  abut  against 
the  first  one.  A  block  can  then  be  set  in  the  angle 
between  the  two,  and  both  foot -boards  can  be  nailed 
to  it.  A  strong  construction  is  secured  in  this  way, 
and  the  joints  between  the  foot -boards  and  the  plat- 
form can  also  be  kept  tight. 

73.  Wire  Netting.  It  is  advisable  to  use  wire 
netting  along  the  side  of  a  scaffold  platform,  wherever 
it  is  practicable  to  do  so.  When  such  netting  is  used 
it  should  be  of  stout  wire,  with  a  mesh  not  more  than 
half  an  inch  square,  and  it  should  extend  from  the 
guard-rail  to  the  toe -board,  or  the  platform,  and  be 
securely  fastened  at  the  top  and  bottom  along  its 
entire  length.  The  wires  should  be  soldered  together 
at  every  intersection. 

The  use  of  wire  netting  is  particularly  important 
upon  suspended  scaffolds  that  are  used  for  construction 
work,  and  this  aspect  of  the  subject  receives  special 
attention  in  paragraph  130.  (See  paragraph  134,  also.) 
In  connection  with  bricklayers'  pole  scaffolds  the  net- 
ting is  less  practicable.  In  the  suspended  scaffold 
it  may  be  attached  once  for  all,  because  the  platform 
is  shifted  as  a  whole;  but  in  the  bricklayers'  pole  scaf- 
fold the  netting  has  to  be  moved  every  little  while, 
when  the  plank  flooring  is  raised  to  the  next  level.  It 
is  no  great  task  to  shift  the  netting,  however,  and  it  is 
advisable  to  use  it  even  upon  the  bricklayer's  scaffold, 
for  the  sake  of  the  increased  safety  that  it  affords.  It 
should  certainly  be  adopted  whenever  there  is  unusual 
danger  of  injury  to  persons  on  the  ground  below,  from 
the  fall  of  materials  from  the  working  platform.  It 
is  advisable  to  use  wire  netting  on  all  the  permanent 
platforms  of  independent  pole  scaffolds, — that  is,  on  the 


136  SPECIAL  SAFETY  FEATURES 


FIG.  57.     PROTECTIVE  PLATFORM  OVER  A  DOORWAY. 


PASSAGEWAYS  AND  WORKPLACES  137 

platforms  that  are  to  remain  fixed  in  position  through- 
out the  work.  Stout  netting  should  also  be  used  along 
the  free  edges  of  sidewalk  sheds  and  protective  plat- 
forms, such  as  are  described  in  paragraphs  148  and  149. 

74.  Auxiliary  Platforms.          When  scaffolds  are 
unusually  high,  or  wiien  the  hazard  to  workmen  and 
to  the  public,  through  the  possible  fall  of  materials, 
is  unusually  great,  wide  auxiliary  platforms  should  be 
provided  at  suitable  places,  to  catch  anything  that 
may  fall  from  the  scaffold.     Platforms  of  this  kind  are 
of  special  importance  in  connection  with  suspended 
scaffolds,  and  further  consideration  of  them  is  therefore 
reserved  for  paragraph  149. 

75.  Protection  over  Passageways  and  Workplaces. 
It  is  highly  important  to  provide  protection  over  door- 
ways and  passages  that  are  used  by  workmen,  when 
wwk  is  going  on  upon  scaffolds  or  wralls  above  them. 
Platforms  for  giving  protection  of  this  kind  should  be 
substantial  enough  to  resist  shocks  due  to  the  fall  of 
fairly  heavy  masses  of  material.     The  planks  should 
be  nailed  in  place  so  that  they  cannot   be  easily  dis- 
placed, and  they  should  fit  against  each  other  tightly. 
They  should  also  extend  up  to  the  wall,  so  that  there 
will  be  no  space  between  them  and  the  wall  for  the  fall 
of  materials. 

A  protective  platform  of  the  kind  here  described 
is  shown  in  Figs.  57  to  59.  The  doorway  that  is  seen 
in  Fig.  57  was  used  continually  by  the  workmen,  and 
teams  were  also  driven  through  it  into  the  building, 
from  time  to  time,  for  the  delivery  of  materials.  The 
stringers,  or  thrust-outs,  that  are  seen  extending  into 
the  building  in  a  nearly  horizontal  position  in  Fig.  58, 
supported  the  platform,  and  were  securely  nailed  to 


138 


SPECIAL  SAFETY  FEATURES 


upright  struts  that  were  solidly  wedged  between  the 
two  floors  of  the  building.  The  struts  also  had  sub- 
stantial cleats  nailed  to  them,  to  assist  in  bearing  any 
stress  that  might  be  thrown  upon  the  platform.  It  will 
be  observed  that  the  platform  was  somewhat  higher 
at  the  outer  edge  than  it  was  where  it  came  in  contact 
with  the  building,  so  that  rolling  objects  would  tend  to 
move  toward  the  building,  instead  of  escaping  over  the 
edge  of  the  platform. 

Fig.  59  shows  this  platform,  as  it  appeared  when 
viewed  from  the  interior  of  the  building  after  it  had 


FIG.  58.     SUPPORT  OF  THE  PLATFORM  SHOWN  IN  FIG.  57. 


PASSAGEWAYS  AND  WORKPLACES 


139 


been  in  use  for  a  short  time.  The  efficiency  and  value 
of  the  platform  is  quite  evident,  for  it  had  become  so 
completely  covered  with  debris,  which  would  otherwise 
have  fallen  to  the  ground  directly  in  front  of  the  door- 
way, that  the  planking  itself  could  hardly  be  seen  at 


FIG.  59.     ILLUSTRATING  THE  IMPORTANCE  OF  THE  PROTECTIVE 

PLATFORM. 


140  SPECIAL  SAFETY  FEATURES 

any  point.  It  is  also  evident  that  a  number  of  the 
objects  that  were  caught  by  the  platform  were  large 
enough  and  heavy  enough  to  have  injured  the  work- 
men severely. 

Workplaces  at  which  men  are  employed  on  the 
ground,  and  which  are  near  scaffolds  or  walls  upon  which 
work  is  being  done,  should  be  provided  with  protection 
similar  to  that  given  by  the  platform  shown  above. 
A  plank  roof,  erected  over  the  workplace  and  supported 
by  stout,  well -braced  supports,  is  usually  the  most 
convenient  means  of  affording  the  desired  protection. 
Far  more  attention  should  be  given  to  shields  of  this 
kind,  because  under  present  conditions  it  is  very  com- 
mon indeed  to  see  men  working  at  mortar  beds  and 
other  places,  close  under  a  scaffold  that  is  in  active  use, 
and  without  the  slightest  protection  from  the  fall  of 
objects  from  above.  This  is  an  unfortunate  and  alto- 
gether improper  method  of  doing  work,  and  many  in- 
juries result  from  it. 


VIII.     GENERAL  FEATURES  AND  OPERATIONS. 

76.  Ladders.  Ladders  that  are  used  in  connection 
with  scaffolds  should  be  sound  and  in  good  condition. 
Their  side-bars  should  preferably  be  made  of  spruce  and 
their  rungs  of  oak,  hickory,  or  ash,  and  every  part  of 
the  ladder  should  be  straight-grained  and  free  from 
defects.  The  rungs  should  be  split  and  shaved  to  size, 
instead  of  being  turned.  The  side-bars  should  be  per- 
fectly smooth,  and  free  from  slivers  or  projecting  points. 
It  is  common  to  see  ladders  in  use  that  have  broken  or 
badly-worn  rungs,  or  rungs  that  have  been  repaired  in 
some  makeshift  or  unworkmanlike  manner.  This  is  a 
mistake,  and  many  accidents  have  resulted  from  the 
use  of  ladders  of  that  kind. 

A  ladder  that  is  to  be  used  for  the  transport  of  ma- 
terials should  not  be  more  than  30  or  35  feet  in  length, 
and  it  should  project  above  the  landing  to  which  it  ex- 
tends by  at  least  five  feet,  so  that  a  man  who  is  about 
to  step  on  or  off  the  ladder  may  have  support  for  his 
hands  in  doing  so.  If  it  becomes  necessary  to  use  a 
ladder  that  will  not  reach  to  such  a  height  above  the 
platform  at  its  upper  end,  stout  strips  should  be  securely 
nailed  to  its  side-bars,  so  that  they  may  extend  to  the 
specified  height ;  but  recourse  should  not  be  had  to  such 
strips  if  a  ladder  of  the  proper  length  can  be  obtained. 

In  placing  a  ladder,  it  is  advisable  to  have  one  of 
its  rungs  come  flush  with  the  platform  to  which  the  lad- 
der leads.  When  this  is  not  practicable,  care  should  be 


142  GENERAL  FEATURES 

taken  to  have  the  rung  that  is  nearest  the  platform 
stand  two  or  three  inches  above  it,  rather  than  below 
it,  because  a  better  footing  can  be  had  in  this  way. 

It  is  more  or  less  common,  in  construction  work, 
to  extend  a  ladder  by  securing  another  one  to  it  at  its 
upper  end,  wrhen  the  height  to  be  surmounted  is  greater 
than  can  be  spanned  by  a  single  ladder  of  convenient 
length.  The  ladders  may  be  united  in  various  ways. 
A  very  strong  connection  can  be  had  by  overlapping 
the  two  for  a  distance  of  five  or  six  feet,  and  lashing 
them  together  with  rope  or  wire  cord.  Considerable 
time  is  required  to  make  a  union  of  this  kind,  however, 
and  a  connection  similar  to  that  shown  in  Fig.  60  is 
therefore  preferred  by  most  American  contractors. 
Ladders  that  are  to  be  united  in  this  way  are  made  with 
their  sides  parallel,  or  nearly  so,  instead  of  tapering 
from  the  bottom  toward  the  top.  Their  side-bars  are 
also  rectangular  in  shape,  instead  of  being  approximate- 
ly semicircular.  The  upper  ladder  is  narrower  than 
the  lower  one,  and  fits  inside  of  it,  as  sho\vn.  The  two 
iron  rungs  by  which  the  ladders  are  united  should  be 
about  one  inch  in  diameter,  threaded  at  both  ends,  and 
fitted  with  nuts  and  with  large,  thick  washers.  In  con- 
necting the  ladders  they  should  be  pushed  together  until 
the  iron  rungs  rest  solidly  against  the  bottoms  of  the 
slots  that  are  provided  to  receive  them,  and  the  nuts 
on  the  ends  of  the  rungs  should  then  be  screwed  up 
solidly. 

It  is  exceedingly  important  to  strengthen  the  side- 
bars of  the  ladders  in  some  effective  way,  so  that  they 
will  not  split  apart  at  the  bottoms  of  the  slots.  This 
is  usually  effected,  as  shown,  by  putting  a  bolt  through 
each  side-bar,  as  close  as  practicable  to  the  bottom  of 


LADDERS 


IRON 


RUNG 


IRON 


RUNG 


FIG.  60.     AN  APPROVED  METHOD  OF  EXTENDING  LADDERS. 

the  slot.  As  the  safety  of  the  construction  depends 
largely  upon  the  soundness  of  the  wood  at  the 
slotted  ends  of  the  ladders,  it  is  also  highly  im- 
portant to  protect  the  side-bars  against  decay,  at  these 
points,  by  coating  them  from  time  to  time  (particu- 
larly on  the  inside  of  the  slots)  with  a  waterproof  pre- 
servative paint. 


144  GENERAL  FEATURES 

A  ladder  that  is  extended  in  this  way,  or  by  any 
other  method,  should  be  securely  and  effectively  braced 
at  the  splice,  and  also  at  any  other  points  that  it  may 
be  necessary  to  support  in  order  to  prevent  the  junction 
from  being  subjected  to  a  bending  stress.  There  should 
be  no  stress  whatever  at  the  splice  but  a  direct  thrust, 
acting  along  the  length  of  the  ladder. 

Ladders  should  never  be  extended  unless  the  exi- 
gencies of  the  work  require  it.  Whenever  practicable 
it  is  far  better  to  arrange  them  in  single  lengths,  with 
a  platform  landing  at  the  head  of  each  ladder,  some- 
what as  shown  in  Fig.  28.  The  ladders  and  their  land- 
ings can  be  seen  in  this  engraving,  though  not  as  clearly 
as  could  be  desired,  inside  of  the  scaffold  frame,  in  the 
panel  in  which  the  central  man  of  the  three  that  are 
shown  is  standing. 

Fig.  32  shows  a  different  disposition  of  the  ladders. 
They  are  exterior  to  the  framework  of  the  scaffold  in 
this  case,  leading  to  platforms  that  rest  upon  outriggers 
and  are  further  supported  by  braces  running  from  their 
outer  edges  to  the  framework  of  the  scaffold.  The 
lower  ladder  in  this  illustration  is  decidedly  longer  than 
we  should  recommend,  but  the  general  arrangement  is 
well  worth  study. 

In  every  case  the  foot  of  the  ladder  should  be  firmly 
secured,  to  prevent  all  possibility  of  slipping,  and  the 
upper  end  should  also  be  fastened  effectively,  so  that 
the  ladder  cannot  slip  sidewise  nor  be  overthrown  by 
being  pushed  bodily  away  from  the  platform  against 
which  it  is  supposed  to  rest.  Ladders  should  be  rigid, 
so  that  they  will  not  spring  to  a  sensible  extent  when  in 
use.  If  they  are  not  stiff  enough  in  themselves  to  fulfil 
this  condition,  they  should  be  supported  at  the  middle 


LADDERS  145 

of  their  length  by  bracing  extending  to  the  framework 
of  the  scaffold  or  to  some  other  fixed  and  solid  object. 
In  Fig.  32  it  will  be  seen  that  the  lower  ladder  is  sup- 
ported midway  of  its  length  by  a  thrust -out  that  is 
lashed  to  the  scaffold  itself. 

Ladders  up  which  materials  are  to  be  transported 
should  be  so  arranged  that  they  do  not  come  one  over 
another,  and  so  that  no  one  of  them  conies  over  a  place 
where  men  are  at  work,  or  where  they  are  likely  to  be 
frequently  passing.  If  it  is  not  possible  to  arrange  the 
ladders  in  this  way,  each  one  of  them  should  be  sheathed 
underneath  by  tacking  on  boards  in  such  a  way  that 
falling  objects  will  be  arrested  by  the  sheathing,  and  be 
prevented  from  crashing  down  upon  the  workplaces 
or  ladders  below.  Helpers  carrying  materials  in  hods 
or  otherwise  should  be  so  handled  that  no  two  of  them 
will  be  on  a  ladder  at  the  same  time.  Serious  accidents 
frequently  occur  from  a  violation  of  this  precaution, 
and  it  is  not  at  all  uncommon,  when  two  men  are  using 
the  same  ladder,  for  the  upper  one  to  fall,  or  let  a  por- 
tion of  his  burden  fall,  and  thereby  knock  the  lower  man 
from  the  ladder.  It  is  best  to  have  at  least  two  ladder- 
ways,  one  to  be  used  exclusively  by  men  going  up,  and 
the  other  exclusively  by  men  going  down.  When  this 
plan  is  in  force  it  is  easier  to  make  the  men  go  up  one  at 
a  time;  because  when  a  single  ladderway  is  used  for 
travel  in  both  directions,  they  naturally  form  the  habit 
of  ascending  with  their  loads  in  gangs  or  groups  of  three, 
four,  or  five,  in  order  to  avoid  confusion  and  delay 
through  meeting  others  who  wish  to  come  down.  (See 
also  paragraph  87.) 

77.  Runways.  Runways  are  exceedingly  con- 
venient for  delivering  materials  to  the  working  plat- 


146 


GENERAL  FEATURES 


forms  of  scaffolds  of  all  kinds,  and  as  they  can  also  be 
made  quite  safe,  we  recommend  the  use  of  them  when- 
ever they  can  be  applied  with  advantage.  They  are 
particularly  well  adapted  to  low  scaffolds,  but  when  the 
space  that  is  available  about  the  base  of  the  scaffold  is 
restricted,  or  must  be  used  for  the  storage  of  materials 
or  for  some  other  important  purpose,  it  is  sometimes 
difficult  to  install  runways.  If  the  runway  is  not  too 
steep,  the  material  can  be  carried  up  in  barrows;  and 
even  when  hods  are  used  it  is  far  easier  and  safer  to 
walk  up  an  inclined  plank  than  to  climb  a  ladder. 


FIG.  61.     RUNWAY  SERVING  AN  INDEPENDENT  POLE  SCAFFOLD. 


RUNWAYS  147 

Runways  should  not  be  unnecessarily  steep,  and 
when,  on  account  of  lack  of  room  or  for  any  other  rea- 
son, they  must  be  made  steeper  than  good  judgment 
would  indicate  to  be  wise  under  other  circumstances, 
they  should  be  provided  with  cleats  running  crosswise 
and  spaced  not  more  than  six  or  eight  inches  apart,  to 
afford  a  secure  footing  for  the  men.  In  the  winter 
the  runways  should  be  kept  free  from  ice  and  snow,  and 
if  they  become  slippery  at  any  time  a  liberal  applica- 
tion of  sand  or  ashes  should  be  made  to  them. 

Runways  should  be  wide  enough  to  avoid  any 
chance  of  accident  from  a  possible  misstep.  If  they 
are  high  above  the  ground,  or  pass  near  deep  holes, 
they  should  be  guarded  by  stout  hand-rails;  and  they 
should  also  be  guarded  by  hand-rails  if  they  pass  over 
or  near  mortar  beds,  railroad  tracks,  high-tension 
electric  wires,  or  other  evident  sources  of  danger. 

In  all  cases  runways  should  be  rigidly  supported 
or  braced,  so  that  they  will  not  yield  sensibly  under  the 
workmen  as  they  pass.  The  planks  should  also  be 
arranged  or  secured  so  that  they  cannot  become  dis- 
placed, either  sidewise  or  endwise.  The  successive 
planks  of  the  platform  may  abut  against  each  other, 
so  as  to  render  the  passageway  as  smooth  as  possible ; 
but  in  this  case  every  plank  should  be  especially  well 
secured,  and  great  care  should  be  taken  to  provide 
a  wide  and  safe  bearing  for  the  ends  where  the  succes- 
sive planks  abut.  If  the  planks  of  the  runway  are 
allowed  to  lap  over  each  other,  then  at  the  lap  the 
plank  that  comes  from  below  should  lie  over  the  one 
that  comes  from  above;  for  if  this  arrangement  is 
adopted,  and  a  workman  should  trip  against  the  over- 
lapping end  of  the  plank,  he  will  trip  when  he  is  going 


148 


GENERAL  FEATURES 


FIG.  62.     TEMPORARY   STAIRWAY   USED   IN  CONNECTION  WITH 

SCAFFOLDING. 

down,  and  therefore  when  he  is  not  carrying  a  load, 
and  he  will  be  better  prepared  to  recover  his  balance 
and  escape  injury.  This  arrangement  of  the  overlap 
is  also  far  more  convenient  than  the  alternative  one, 
wrhen  the  material  is  transported  in  barrows. 


STAIRWAYS  149 

78.  Stairways.     When  a  scaffold  is  to  be  used 
for  a  considerable  time,  it  is  best  to  build  stairways 
for  the  use  of  the  workmen.     Fig.  62  shows  a  temporary 
stairway  that  was  erected  for  the  use  of  the  workmen 
in  connection  with  the  construction  of  a  building.     This 
stairway  was  in  the  interior  of  the  building,  and  gave 
access  to  the  scaffolds  from  the  inside.     It  will  be  seen 
that  the  inclination  of  the  stairway  was  moderate  and 
convenient,  and  that  the  height  of  the  treads  was  like- 
wise chosen  with  a  view  to  making  the  ascent  as  easy 
as   possible.      A   substantial  hand-rail  was  provided 
on  each  side;  and  the  whole  was  stiffened  by  supports, 
one  of  which  is  plainly  seen  on  the  right,  connecting 
with  the  stairway  itself  and  also  with  the  railing,  and 
resting  against  the  floor  of  the  building  at  its  lower 
end. 

An  excellent  arrangement  of  stairways,  external 
to  the  building,  is  shown  in  Fig.  63,  which  is  from  a 
large  model  in  the  safety  museum  at  Charlottenburg, 
Germany.  As  will  be  seen,  there  are  four  successive 
flights  of  stairs,  and  each  one  is  provided  with  a  double 
guard-rail,  and  braced  at  its  middle  point  so  as  to  be  as 
rigid  as  possible.  The  landings  are  substantially  con- 
structed, and  each  one  has  a  broad  foot -board,  and  two 
guard-rails  that  are  supported  by  braces  running  at 
an  angle  of  45°  to  the  outriggers  upon  which  the  plat- 
form rests.  The  outriggers  are  also  supported  by  diag- 
onal braces  that  run  to  the  framework  of  the  scaffold. 
Each  of  these  stairways  is  sheathed  underneath. 

79.  Nails.     For  scaffold  work,  cut  nails  of  large 
size  and  of  the  finest  quality  should  always  be  used, 
and  wire  nails  should  never  be  employed.     The  nails 
that  are  used  in  scaffold  work  are  often  brittle,  and 


150 


GENERAL  FEATURES 


FIG,     63.     SCAFFOLD 


STAIRWAYS     WITH 
LANDINGS. 

(From  a  large  model.) 


RAILED     PLATFORM 


NAILS  151 


FIG.  64.     SCAFFOLD  NAILS,   TESTED  BY  BENDING  AROUND   AN 

ARBOR. 

therefore  dangerous.  Every  lot  of  nails  that  is  bought 
for  this  purpose  should  be  thoroughly  tested,  and  if  the 
sample  nails  that  are  selected  do  not  satisfactorily  stand 
the  test,  the  whole  lot  should  be  rejected,  or  used  for 
some  other  purpose  where  strength  is  not  a  primary 
consideration. 

Fig.  64  shows  that  nails  of  very  fine  quality  can  be 
had,  if  a  little  trouble  is  taken  in  selecting  them.  These 
nails  were  twisted,  cold,  around  a  cylindrical  rod  about 
1/4  in.  in  diameter,  and  they  stood  the  test  without  the 
slightest  sign  of  fracture. 

A  rough  but  useful  and  easy  method  of  testing  nails  in 
judging  their  suitability  for  scaffold  work  consists  in  driv- 
ing them  half-way  into  a  block  of  wood,  and  then  work- 
ing them  back  and  forth  through  a  full  right  angle  with 
the  claw  of  a  hammer, — bending  them  three  times  in  each 
direction.  If  they  stand  this  treatment  without  evidence 
of  distress  they  may  be  considered  to  be  satisfactory. 


152  GENERAL  FEATURES 

Builders  of  scaffolds  sometimes  leave  the  heads  of 
the  nails  projecting  somewhat,  so  that  they  can  be  more 
easily  removed  in  taking  the  scaffold  down.  We  con- 
sider this  to  be  unwise,  inasmuch  as  it  weakens  the 
structure  to  some  extent,  even  when  nails  of  extra 
length  are  employed.  The  nails  should  always  be 
driven  solidly  home. 

80.  Dismantling  Pole  Scaffolds.  The  work  of 
dismantling  a  pole  scaffold  should  be  intrusted  only 
to  experienced  men,  who  understand  this  part  of  the 
operation  and  who  have  served  as  complete  an  appren- 
ticeship as  possible  at  it.  The  dismantling  should  be 
done  in  an  orderly  manner,  beginning  at  the  top  of  the 
scaffold  and  proceeding  downward  systematically. 
The  braces  should  be  left  in  position  as  long  as  pos- 
sible, so  that  at  every  stage  of  the  process  the  part  of 
the  scaffold  that  still  remains  standing  may  be  secure. 
For  a  discussion  of  various  other  important  points,  see 
paragraph  159, 


IX.     BUILDING  WITH  HORSES. 

81.  Use  of  Horses.  The  masons'  horse  is  widely 
used  in  the  construction  of  buildings,  both  on  the  inside 
and  on  the  outside  of  the  wall.  Its  use  externally  is 
becoming  less  common  than  formerly,  however. 

When  horses  are  used  in  laying  a  wall  from  the 
inside,  the  floors  of  the  building  should  be  put  in  as  the 
wall  goes  up, — substantial  temporary  flooring  being 
laid  if  it  is  not  convenient  to  put  in  the  permanent 
floors,  at  the  time.  The  wall  can  be  carried  up  to 
a  height  of  about  five  feet  from  a  floor  without  horses, 
and  when  this  has  been  done  horses  are  arranged  along 
the  wall  and  covered  over  with  planks,  so  as  to  provide 
an  elevated  platform  from  which  the  wall  is  carried 
up  by  another  five  feet.  If  the  height  of  the  room  in 
which  the  work  is  done  calls  for  it,  a  second  tier  of  horses 
is  then  erected  upon  the  platform  that  was  laid  upon 
the  first  tier,  a  new  platform  is  laid  at  the  higher  level, 
and  the  work  proceeds  as  before.  When  the  wall  has 
reached  the  height  of  the  next  floor,  the  procedure 
varies  to  some  extent  according  to  the  nature  of  the 
building.  If  it  has  a  steel  skeleton,  and  the  floors  are 
already  laid,  the  bricklayers  merely  go  up  one  story 
and  repeat  the  operation  already  described.  If  there 
is  no  such  skeleton,  the  building  of  the  wall  is  suspended 
for  a  time,  while  another  course  of  beams  is  put  in  place 
and  a  new  floor  is  laid  (either  permanently  or  tempo- 
rarily) ;  after  which  the  work  proceeds  as  before. 


154  BUILDING  WITH  HORSES 

The  materials  that  are  to  be  used  in  building  the 
wall  can  be  easily  passed  up  by  hand  when  only  one 
tier  of  horses  is  in  use.  When  there  are  two  or  more 
tiers,  material  may  be  delivered  to  the  working  level, 
by  hand,  in  successive  stages, — being  passed  first  to 
the  lowest  platform,  then  to  the  one  next  above,  and 
so  on.  It  may  also  be  carried  up  ladders  in  hods,  in  the 
usual  way;  and  when  it  is  practicable  to  use  them,  run- 
ways are  recommended,  consisting  of  inclined  planks 
up  which  the  material  can  be  carried  in  hods  or  wheeled 
in  barrows. 

If  the  material  is  to  be  passed  up  in  successive 
stages,  as  first  described,  it  is  well  to  have  each  platform 
at  least  three  feet  wider  than  the  one  immediately  above 
it,  in  order  that  the  helpers  may  have  an  opportunity 
to  work  freely  and  without  danger  of  falling. 

82.  Design  and  Condition  of  Horses.  All  horses 
that  are  used  for  building  purposes  should  be  solid  in 
construction,  and  of  good  design.  They  should  be  made 
of  sound,  selected  material,  and  should  be  braced 
internally  so  as  to  be  rigid  enough,  not  only  to  carry 
their  normal  vertical  load  with  safety,  but  also  to  resist 
deformation  from  sidewise  thrusts. 

Horses  should  not  have  their  legs  set  at  too  wide 
an  angle,  because  this  makes  them  structurally  weak 
and  likely  to  spread  under  their  loads.  Nor,  on  the 
other  hand,  should  they  be  too  acute  (or  narrow)  in 
the  legs,  because  this  lessens  their  stability.  (As  an  ex- 
ample of  a  horse  with  legs  set  at  too  small  an  angle,  see 
the  one  nearest  the  center  of  Fig.  67.)  Experience  has 
shown  that  the  proportions  indicated  in  Fig.  65  are 
about  the  best  that  can  be  had.  The  angle  between 
the  legs,  here,  is  approximately  22  1/2°,  and  the  dis- 


DESIGN  AND  CONDITION  OF  HORSES 


155 


tance  from  one  leg  to  the  other  therefore  increases  by 
about  43/4  inches  for  each  foot  of  vertical  height. 

Horses,  the  parts  of  which  have  become  loosened 
or  weakened  in  any  way  whatsoever,  should  not  be  used 
until  they  have  been  repaired  in  a  thorough  and  work- 
manlike manner;  and  repairing  should  not  be  done  to 
an  excessive  extent,  because  it  is  much  better  to 
discard  a  horse  altogether,  and  replace  it  with  a  new 
and  sound  one,  than  it  is  to  spend  an  unreasonable 
amount  of  time  in  patching  up  one  that  is  old  and 
weakened. 


FIG.  65.     A  WELL-DESIGNED  HORSE 


156  BUILDING  WITH  HORSES 

83.  The  Platforms  on  the  Horses.  The  planking 
upon  the  horses  should  be  carefully  laid,  and  the  planks 
should  have  their  edges  in  close  contact  with  each  other, 
so  that  tools  and  materials  cannot  fall  down  between 
them.  They  should  also  be  laid  so  that  an  accident 
from  the  tipping  of  a  plank  shall  be  impossible.  The 
horses  should  be  near  enough  together  to  support  the 
planks  properly,  and  to  prevent  them  from  springing 
at  the  middle.  This  condition  ordinarily  calls  for  at 
least  three  horses  under  every  plank,  one  being  placed 
at  each  end,  and  one  or  more  in  the  middle.  Care 
should  also  be  taken  to  see  that  the  planks  actually 
bear  against  the  middle  horse  or  horses,  so  that  they 
receive  a  real  support  there,  effective  enough  to  prevent 
all  springing  of  the  platform.  In  order  to  fulfil  this 
condition,  workmen  commonly  put  pieces  of  brick 
or  tile  under  the  legs  of  some  of  the  horses,  to  bring 
them  up  to  the  proper  height.  All  four  legs  of  the 
horse  immediately  over  the  doorway  in  the  center  of 
Fig.  66,  for  example,  were  resting  upon  bricks.  Sup- 
port of  this  kind  should  never  be  permitted,  because  the 
stability  of  the  scaffold  may  be  seriously  imperiled 
by  such  makeshift  arrangements.  If  a  horse  is  not 
quite  high  enough  to  afford  a  proper  support  to  the 
planking,  it  should  be  placed  so  that  its  legs  rest 
directly  and  solidly  upon  the  platform  below,  and  a 
wooden  strip  of  the  proper  thickness  should  be  laid 
upon  the  top  of  the  horse  and  securely  nailed  in 
position. 

A  horse  scaffold  is  not  adapted  to  the  support  of 
heavy  loads,  and  it  should  never  be  used  for  the  storage 
of  considerable  quantities  of  material.  If  the  conditions 
are  such  that  a  heavier  load  than  usual  must  be 


HORSES  IN  TIERS  157 

carried,  it  is  better  to  provide  two  horses  between  the 
ends  of  the  planks  instead  of  one ;  and  in  all  cases  the 
number  and  construction  of  the  horses,  and  the  design 
and  construction  of  the  whole  scaffold,  must  be  adapted 
to  the  load  that  is  to  be  carried,  taking  account  of  the 
weight  of  the  workmen  as  well  as  of  that  of  the  materials. 

84.  Use  of  Horses  in  Tiers.  In  making  use  of 
horses  for  erecting  walls  from  the  inside  of  a  building 
it  is  seldom  necessary  to  have  more  than  two  or  three 
tiers  of  them.  This  will  give  a  height  at  least  as  great 
as  the  height  of  an  ordinary  room,  and  when  the  wall 
has  been  put  up  one  story  the  horses  are  shifted  to  the 
next  floor  above.  When  the  work  is  done  in  this  way, 
and  the  permanent  floors  are  laid  or  the  beams  are 
properly  covered  with  planks  as  the  work  proceeds,  the 
danger  of  serious  injury  from  falls  is  not  great,  if  the 
horse  scaffold  is  built  with  care.  Many  contractors, 
however,  use  horse  scaffolds  for  outside  work,  building 
them  up,  sometimes,  to  a  height  of  six  or  eight  tiers. 
We  strongly  recommend  some  other  form  of  scaffold 
in  cases  like  this,  because  the  horse  scaffold  is  by  nature 
less  solid  and  stable  than  other  types  that  can  easily  be 
had.  If  it  is  used  in  such  cases,  it  should  be  constructed 
with  great  care. 

In  putting  up  successive  tiers  of  horses,  each  horse 
should  come  directly  and  squarely  above  one  in  the 
next  row  below,  because  this  insures  the  best  possible 
distribution  of  stress  in  the  planking,  and  it  also  tends 
to  give  the  maximum  degree  of  solidity  and  stability  to 
the  structure  as  a  whole. 

Some  of  the  points  that  we  desire  to  make  will  be 
better  understood  by  reference  to  Fig.  66,  which  shows 
a  horse  scaffold  that  is  erected  in  a  way  that  does 


158 


BUILDING  WITH  HORSES 


not  commend  itself  to  the  safety  engineer,  although 
work  of  this  character  is  very  common.  It  \vill  be 
seen,  for  example,  that  although  the  principle  of  hav- 
ing the  horses  stand  squarely  over  one  another  is 
roughly  fulfilled  on  the  right  of  the  engraving,  it  is 
flagrantly  violated  on  the  left.  Furthermore,  it  is 
poor  construction  to  allow  horses  to  rest  upon  the 
middle  of  a  platform  that  is  supported  only  at  the  ends, 
as  seen  in  the  central  part  of  the  engraving,  where 
three  tiers  of  horses  are  supported  by  the  middle  of 
the  planking  over  the  door.  It  is  true  that  the  sup- 
porting planks  are  double;  but  although  this  doubling 
is  helpful,  a  construction  like  the  one  shown  is  weak, 
and  the  spring  of  the  supporting  planking  makes  all 
the  platforms  above  it  insecure. 


FIG.  66.     AN  IMPROPERLY-CONSTRUCTED  HORSE  SCAFFOLD 


HORSES  IN  TIERS 


159 


Fig.  67  shows  a  method  that  workmen  employ  very 
commonly,  for  increasing  the  height  of  the  working 
level  by  a  couple  of  feet  or  so,  when  using  horse  scaffolds. 
Small  supporting  piers  are  built  of  brick  or  tile,  or  of 
other  objects  that  may  be  handy,  and  on  the  top  of  these 
a  few  planks  are  laid.  The  little  piers  are  sometimes 
fairly  safe,  but  far  oftener  they  are  so  insecure  that  it  is 
hard  to  understand  why  the  men  are  willing  to  trust  to 
them. 

If  a  small  increase  in  elevation  like  this  is  desired, 
to  facilitate  the  work,  it  is  much  better  to  provide  a  few 
well-made  horses  of  half  the  usual  height,  and  somewhat 
shorter  than  the  ordinary  horse.  This  not  only  pro- 
motes safety,  but  also  saves  money  in  the  end,  because 
a  considerable  amount  of  time  is  required  to  build  and 
remove  the  piles  of  material  that  the  men  ordinarily  use. 


FIG.  67.     A  MAKESHIFT  METHOD  OF  INCREASING  THE  HEIGHT 
OF  THE  WORKING  PLATFORM. 

(From  a  horse  scaffold  at  Lausanne,  Switzerland.) 


160  BUILDING  WITH  HORSES 

85.  Security  of  the  Horses.  This  subject  has  al- 
ready been  considered  in  certain  aspects  in  paragraphs 
83  and  84,  to  which  reference  should  therefore  be  made. 
In  the  present  paragraph  we  take  up  a  few  additional 
points. 

All  that  was  said  in  the  earlier  paragraphs  against 
the  use  of  bricks  and  tiles  under  the  legs  of  the  horses, 
for  the  purpose  of  bringing  their  upper  parts  to  the 
proper  level,  applies  with  special  force  to  the  lowest  row 
of  a  tier  of  horses;  because  extra  care  should  be  taken 
to  see  that  the  horses  have  a  firm  and  absolutely  solid 
foundation  to  rest  upon,  in  every  case.  The  lowest  tier 
of  horses  should  not  be  allowed  to  stand  in  direct  contact 
with  the  earth,  but  should  be  made  to  rest  upon  large 
sections  of  stout  plank,  that  will  prevent  them  from  sink- 
ing into  the  ground.  The  legs  are  almost  certain  to 
sink  in  unequally  if  this  precaution  is  not  taken,  so  that 
there  is  a  poor  distribution  of  stresses  in  the  scaffold, 
and  in  a  bad  case  it  may  even  topple  over,  bodily.  The 
use  of  bricks  or  tiles  for  a  foundation,  in  the  place  of 
the  sections  of  plank  recommended  above,  should  not 
be  permitted,  because  in  many  cases  they  are  \vholly 
inadequate. 

Horses  should  never  be  allowed  to  rest  merely  upon 
beams  or  joists,  nor  should  they  be  erected  in  any  man- 
ner that  would  be  likely  to  lead  to  a  fall  in  case  of  a 
displacement  such  as  might  occur  in  the  course  of  the 
work.  Each  tier  of  horses  should  preferably  be  entirely 
covered  with  planking,  though  it  is  an  almost  universal 
custom  to  use  only  two  rows  of  planks  on  all  the  horses 
except  those  of  the  topmost  tier, — one  row  at  the  front 
and  one  at  the  back,  to  support  the  legs  of  the  horses 
next  above.  When  horses  are  used  on  the  inside  of  a 


SECURITY  OF  THE  HORSES  161 

wall,  a  stout  temporary  flooring  of  planks  should  be 
laid  to  support  them,  as  previously  explained,  if  the 
permanent  floor  is  not  already  laid  when  the  wall  reaches 
its  level.  If  the  floor  is  of  concrete,  or  of  tile  and  mortar, 
it  should  also  be  allowed  to  set  thoroughly,  before  the 
weight  of  the  horses  is  allowed  to  come  upon  it.  The 
legs  of  the  bottom  horses  of  a  scaffold  should  not  be 
allowed  to  rest  directly  upon  the  tiles  of  floor  arches, 
in  any  event. 

On  all  scaffolds  more  than  two  tiers  high  the  legs 
of  the  horses  should  be  tacked  down  sufficiently  to 
prevent  any  horse  from  shifting  as  the  result  of  wind 
pressure,  the  thrust  of  ladders  (see  paragraph  87),  the 
accumulated  effect  of  repeated  small  motions,  or  other 
causes. 

Fig.  68  shows  a  horse  scaffold  supported  by  thrust- 
outs  projecting  from  the  interior  of  the  building  upon 
which  the  scaffold  was  used.  It  will  be  seen  that  the 
horses  of  the  second  tier  stand  directly  over  those  of  the 
first  tier  in  nearly  every  case.  This  feature  of  the  con- 
struction is  commendable,  but  we  do  not  favor  the  use 
of  horses  in  the  way  here  shown,  where  a  fall  would 
probably  be  fatal.  If  horses  must  be  supported  upon 
thrust-outs  in  this  way,  they  should  be  securely  nailed  to 
the  planks  upon  which  they  rest,  and  the  planks  should 
also  be  nailed  in  place  very  firmly.  The  whole  structure 
in  fact,  should  be  made  as  solid  as  possible.  Guard- 
rails and  foot -boards  should  also  be  provided,  as  describ- 
ed in  paragraph  89. 

When  a  tier  of  horses  is  to  be  erected  upon  one  that 
is  already  in  position,  the  planking  over  the  lower  tier 
should  be  carefully  placed,  and  the  horses  of  the  next 
higher  one  should  be  set  so  that  their  legs  will  rest 


162 


BUILDING  WITH  HORSES 


solidly  and  completely  upon  the  platform  that  is  to  sup- 
port them.  In  the  interest  of  increased  safety,  and  to 
facilitate  the  delivery  of  materials,  the  lower  platforms 
of  horse  scaffolds  are  sometimes  made  much  wider  than 
the  higher  ones.  This  construction  is  often  advanta- 
geous; but  when  it  is  adopted  the  support  of  the  exten- 


FIG.  68.     A  HORSE  SCAFFOLD  SUPPORTED  ON  OUTRIGGERS   OR 
THRUST-OUTS. 


BRACING  HORSE  SCAFFOLDS  163 

ded  part  of  the  lower  and  wider  platforms  is  frequently 
neglected,  totally  inadequate  provision  being  made  for 
its  stability.  The  extension  platforms  should  receive 
the  same  care  that  is  given  to  those  that  lie  next  to 
the  wall. 

Horses  are  sometimes  set  upon  a  narrow  platform 
by  turning  them  around  somewhat  so  that  they  stand 
obliquely  (or  diagonally)  to  the  wall.  If  a  horse  is 
turned  to  a  sufficient  angle,  all  four  of  its  legs  may  be 
brought  to  bear  upon  a  platform  that  is  much  narrower 
than  the  length  of  the  horse.  When  this  method  of 
erection  is  followed,  however,  one  or  more  of  the  legs 
of  the  horse  are  often  left  projecting  partially  or  wholly 
over  the  edge  of  the  supporting  platform,  so  that  a 
slight  displacement  would  throw  the  scaffold  down,  with 
serious  consequences  to  the  workmen.  Furthermore, 
when  horses  are  arranged  in  this  way  the  ends  of  some 
of  the  planks  that  they  support  often  project  to  a  con- 
siderable distance  beyond  some  part  of  the  oblique 
horses,  so  that  there  is  danger  of  the  platform  tipping  up 
when  a  load  is  placed  upon  it,  or  even  when  a  man  steps 
upon  it.  It  is  much  better  and  safer  to  make  all  the 
platforms  of  proper  width,  so  that  the  horses  can  stand 
upon  them  squarely  and  securely.  The  loss  of  time 
required  to  lay  them  in  this  way  is  far  more  than  com- 
pensated by  the  increased  security. 

86.  Shoring  and  Bracing  Horse  Scaffolds.  When 
horses  are  set  tier  upon  tier,  the  stability  of  the  structure 
diminishes  quite  rapidly  as  the  height  increases.  As  a 
rule,  the  instability  is  already  quite  noticeable  when 
there  are  three  tiers,  the  upper  platform  being  no  longer 
solid  under  foot,  but  yielding  to  some  extent,  with  a 
rocking  motion,  as  the  workmen  move  about.  The 


164  BUILDING  WITH  HORSES 

horses  are  sometimes  carried  to  a  much  greater  height 
than  this,  and  as  many  as  six  or  eight  tiers  of  them  may 
occasionally  be  seen,  with  a  marked  increase  of  insta- 
bility. We  do  not  recommend  the  use  of  horse  scaffolds 
of  so  great  a  height;  but  if  they  are  employed,  every 
horse  should  be  nailed  to  the  planks  that  it  supports,  and 
to  those  upon  which  it  rests.  It  is  also  highly  important 
to  brace  the  whole  structure  in  some  very  substantial 
way.  The  best  way  to  effect  the  bracing  will  vary  with 
the  conditions  under  which  the  scaffold  is  used,  but  in 
most  cases  it  is  best  to  run  shores  to  the  horses,  and  to 
give  them  additional  support  by  means  of  window 
braces.  (Compare  paragraphs  48,  49,  and  56.)  A  shore 
may  be  seen  on  the  right  of  Fig.  66,  running  up  to  one 
of  the  horses,  and  some  of  the  other  horses  are  also 
secured  by  braces  extending  into  the  building  through 
the  window  openings.  These  features  are  good,  but 
the  bracing  of  this  scaffold  is  not  as  complete  and  effec- 
tive as  it  should  be. 

87.  Ladders  on  Horse  Scaffolds.  When  ladders 
rest  against  horses  or  horse  platforms,  the  same 
general  precautions  should  be  taken  that  are  recom- 
mended in  connection  with  ladders  in  other  situations, 
and  which  are  specified  elsewhere.  (See  paragraph 
76,  in  particular.)  It  should  be  remembered,  further- 
more, that  a  ladder  that  is  supporting  a  load  exerts  an 
appreciable  horizontal  thrust  upon  the  object  against 
which  it  rests.  Thus,  a  ladder  inclined  at  an  angle  of 
70  degrees  with  the  ground  (or  20  degrees  with  the 
vertical)  may  exert  a  horizontal  thrust  as  great  as  36 
per  cent,  of  the  weight  of  the  man  and  load  upon  it,  in 
addition  to  whatever  thrust  there  may  be  from  the 
weight  of  the  ladder  itself.  This  means  that  when  a 


GUARD-RAILS  AND  FOOT-BOARDS  165 

man  weighing  160  pounds  is  carrying  a  load  of  60 
pounds  up  a  ladder  inclined  as  we  have  supposed,  the 
horizontal  push  of  the  ladder  against  the  object  that 
sustains  it  at  the  top  may  be  80  pounds;  and  if  the 
ladder  rests  against  a  horse  scaffold,  we  may  therefore 
expect  the  whole  structure  to  fall  down,  if  a  horizontal 
push  of  80  pounds,  applied  at  the  top,  would  suffice  to 
overthrow  it.  This  example  is  given  for  the  purpose 
of  illustrating  the  principle  that  is  involved,  and  to  call 
attention  to  the  importance  that  the  thrust  of  the 
ladder  may  have.  As  a  rule,  however,  the  ladders  that 
are  used  in  a  case  of  this  kind  tend  to  push  the  scaffold 
against  the  wall,  so  that  there  is  no  danger  of  immediate 
overthrow.  Repeated  passing  up  and  down  the  ladder 
may  cause  enough  motion,  however,  to  seriously  disturb 
the  structure  in  the  course  of  time,  and  make  it  insecure. 
Where  a  ladder  rests  against  a  horse  scaffold,  it  should 
come  as  close  as  practicable  to  a  horse,  and  the  plank 
against  which  it  rests  should  be  firmly  nailed  down. 
The  horses  that  support  this  plank  should  also  be 
nailed  to  the  planks  upon  which  they  stand. 

88.  Runways.     Runways  are  often  efficient  and 
convenient,  for  delivering  materials  to  horse  scaffolds 
of  moderate  height.     A  runway  applied  in  this  way 
is  shown  in  Fig.  67.     (For  the  general  principles  that 
should  govern  the  design  and  construction  of  such  run- 
ways, see  paragraph  77.) 

89.  Guard-rails    and    Foot-boards.      Guard-rails 
and  foot -boards  are  seldom  used  upon  horse  scaffolds, 
because  it  is  usually  thought  that  scaffolds  of  this  type 
do  not  lend  themselves  well  to  such  treatment.     These 
important  protective  features  can  be  applied  to  horse 
scaffolds  without  any  great  trouble,  however,  and  the 


166 


BUILDING  WITH  HORSES 


almost  universal  omission  of  them  is  due  far  more  to 
our  American  indifference  to  safeguards,  than  to  any 
real  difficulty  that  is  involved.  In  erecting  a  guard- 
rail on  a  horse  scaffold,  a  piece  of  scantling,  2  inches  by 
4  inches,  should  be  solidly  secured  to  the  side  of  the  pro- 
jecting end  of  the  beam  (or  top  piece)  of  the  horse  by 
three  or  four  nails  of  generous  size,  as  indicated  at  A 
in  Fig.  69,  to  serve  as  an  upright  or  post.  The  lower 
end  of  this  post  should  rest  against  the  end  brace  of  the 
horse,  at  B,  and  be  nailed  to  it.  The  guard-rail  and 
foot-board  can  then  be  erected  as  shown.  Guard-rails 
and  foot -boards  of  this  general  nature  should  be  provi- 
ded on  all  horse  scaffolds  that  are  three  tiers  high  or 
more,  because  it  is  a  simple  matter  to  install  them,  and 


FIG.   69. 


SHOWING  A  GUARD-RAIL  AND  A  FOOT-BOARD,    ox 
HORSE  SCAFFOLD. 


PROTECTION  OF  WORKMEN  167 

they  may  prevent  serious  accidents.  When  another 
tier  of  horses  is  to  be  erected,  the  posts  and  rails  should 
be  removed  from  the  horses  to  which  they  have  been 
attached,  and  nailed  to  the  new  tier  in  like  manner. 

90.  Protection  of  Workmen  Below.  Provision 
for  the  protection  of  persons  who  may  be  working  or 
passing  upon  the  ground  nearly  under  a  horse  scaffold 
is  important  under  all  circumstances,  but  it  is  particu- 
larly so  when  foot-boards  and  guard-rails  are  not  used. 
Careful  attention  should  therefore  be  paid  to  the  sugges- 
tions made  in  paragraph  75. 


X.     SUSPENDED    SCAFFOLDS    FOR    CON- 
STRUCTION WORK. 

91.  Nature  of  the  Suspended  Scaffold.     The  sus- 
pended scaffold,  as  used  in  construction  work  and  in 
making  repairs  and  alterations  about  buildings,  con- 
sists essentially  of  a  platform  that  is  hung  from  over- 
head supports  by  means  of  wire  cables  or  steel  straps, 
and  which  can  be  raised  with  more  or  less  ease  as  the 
work  proceeds,  so  that  the  bricklayers  may  always  stand 
at  a  convenient  height  with  respect  to  the  part  of  the 
wall  upon  which  the  work  is  being  done. 

The  suspended  scaffold,  as  now  employed  by 
builders,  was  evolved  from  the  familiar  light  swinging 
staging  that  is  in  common  use  among  painters,  by 
modifying  the  various  parts  so  as  to  adapt  them  to  the 
heavier  loads  that  have  to  be  supported,  and  to  the 
greater  number  of  workmen  that  must  be  accommo- 
dated in  order  to  carry  on  the  work  of  construction 
efficiently  and  rapidly. 

92.  Limited  Applicability  of  the  Suspended  Scaf- 
fold.    Since  the  suspended  scaffold  is  supported  from 
above,  it  can  be  used,  in  new  work,  only  upon  buildings 
that  have  steel  or  concrete  skeletons,  to  which  the  over- 
head ends  of  its  cables  or  straps  can  be  attached. 

It  is  seldom  economical  to  use  the  suspended  scaf- 
fold for  buildings  that  are  less  than  four  or  five  stories 
in  height.  For  lower  ones  it  is  usually  cheaper  to  use 
the  forms  described  in  the  third  and  fourth  sections 


SUSPENDED  SCAFFOLDS 


169 


•III 


FIG.  70.     THE  CLARK  SCAFFOLD. 

(The  platform  is  supported  by  perforated  steel  strips  or  ribbons.) 


170  SUSPENDED  SCAFFOLDS 

of  this  treatise  (pages  38  and  83) ;  but  for  the  high 
modern  buildings  that  are  popularly  known  as  "sky- 
scrapers" nothing  can  compete  with  the  suspended 
scaffold,  when  it  is  correctly  applied,  either  for  econo- 
my or  for  safety  to  the  workmen. 

The  suspended  scaffold  is  most  commonly  em- 
ployed for  the  laying  of  brick  or  terra  cotta,  though 
it  may  also  be  used  for  riveting  and  various  other 
purposes.  It  is  less  frequently  used  in  the  construction 
of  stone  buildings,  because  in  working  with  stone  the 
blocks  are  ordinarily  raised  and  swung  into  position 
by  derricks  or  other  forms  of  hoisting  apparatus,  and 
as  these  would  interfere  with  the  suspended  platform 
and  its  cables,  the  stone  is  usually  laid  by  the  workmen 
from  the  inside  of  the  building. 

93.  Advantages  of  Suspended  Scaffolds.  Several 
marked  advantages  are  claimed  for  the  suspended 
scaffold  as  a  means  of  handling  and  laying  brick  upon 
lofty  buildings  with  steel  frames,  and  when  the  proper 
conditions  are  fulfilled  there  can  be  no  doubt  that  these 
claims  are  justified. 

The  work  of  construction  is  facilitated,  not  only 
because  the  adjustment  of  the  platform  of  the  scaffold 
is  capable  of  continuous  variation  so  that  the  brick- 
layer can  always  work  at  a  convenient  height,  but  also 
because  the  system  possesses  great  flexibility  and 
adaptability.  It  is  not  necessary  to  delay  the  brick- 
laying until  the  skeleton  is  complete,  and  in  fact  it  is 
the  common  practice  to  begin  this  part  of  the  work 
when  the  framework  has  gone  up  to  a  height  of  about 
100  feet,  the  bricklaying  and  the  structural  steel  work 
thereafter  going  on  together.  Moreover,  the  laying 
of  the  brick  can  begin  at  any  story,  and  this  is  a  marked 


ADVANTAGES  OF  SUSPENDED  SCAFFOLDS  171 

advantage  when  the  various  levels  of  the  building  are 
to  be  faced  with  different  materials,  and  the  kind  that 
is  to  be  used  for  the  lower  stories  is  not  at  hand,  while 
that  required  for  the  upper  ones  is  ready  to  be  set  in 
place.  The  walls  of  the  upper  stories  can  be  laid 
first,  when  using  a  suspended  scaffold,  and  the  lower 
ones  can  be  filled  in  when  the  delayed  material  arrives. 
Examples  of  this  are  often  seen  in  the  erection  of  high 
buildings.  (See  Fig.  94,  on  page  241.) 

The  great  flexibility  of  the  suspended  scaffold  is 
another  marked  advantage.     If  the  laying  of  the  wall 


FIG.  71.     THE  FOSTER  SCAFFOLD. 

(The  putlogs  are  supported  by  steel  cables,  and  are  held  in  place  by  clips.) 


172  SUSPENDED  SCAFFOLDS 

must  proceed  unevenly  for  any  reason,  the  platform  can 
be  raised  where  the  work  is  proceeding  most  rapidly 
and  can  be  kept  at  a  lower  elevation  elsewhere.  It  is 
capable  of  continuous  adjustment  (at  all  events  in 
those  forms  in  which  it  is  supported  by  cables  running 
over  drums),  so  that  the  men  can  always  work  at  a 
convenient  level.  This  tends  to  facilitate  the  whole 
operation,  and  it  also  helps  the  men  to  lay  a  wall  having 
a  neat  appearance  when  done.  For  this  last  reason, 
suspended  scaffolds  are  often  used  for  the  fronts  or 
exposed  sides  of  buildings,  even  when  the  other  walls 
are  put  up  by  other  methods. 

Viewed  from  the  standpoint  of  safety,  the  sus- 
pended scaffold  leaves  little  to  be  desired  when  it  is 
properly  designed,  constructed,  inspected,  and  handled. 
A  good  steel  cable  under  a  reasonable  direct  tension 
is  by  nature  much  more  trustworthy  than  a  long  wooden 
pole  or  column  under  compression.  Moreover,  the 
likelihood  of  damage  to  the  scaffold  from  unforeseen 
extraneous  causes  is  reduced  to  a  minimum  by  sus- 
pending the  platform  from  above,  as  was  forcefully 
illustrated  at  the  time  of  the  fearful  gas  explosion  in  the 
yards  of  the  Grand  Central  Station  in  New  York  City, 
on  December  19,  1910.  Twelve  persons  were  killed 
by  this  explosion  and  106  were  injured.  A  suspended 
scaffold  that  was  almost  directly  over  the  place 
where  the  explosion  occurred  was  severely  shaken 
by  it,  but  the  fifty  workmen  on  the  platform  of 
the  scaffold  were  merely  thrown  from  their  feet, 
and  none  of  them  received  more  than  trifling  in- 
juries. If  the  scaffold  had  been  of  the  pole  type, 
it  is  exceedingly  probable  that  many  deaths  would 
have  resulted. 


THE  TWO  MAIN  TYPES 


173 


There  is  also  less  likelihood  of  injury  to  the  men 
in  the  normal  routine  work  about  a  suspended  scaffold, 
because  when  it  is  properly  installed  and  handled  there 
is  but  little  climbing  about  to  be  done  in  dangerous 
places,  and  but  little  exposure  to  hazards  of  any  kind, 
save  those  that  depend  upon  the  strength  of  the  scaffold 
itself,  and  upon  the  falling  of  tools  and  materials;  and 
all  these  sources  of  danger  can  be  minimized  almost 
to  the  vanishing  point  by  the  exercise  of  reasonable 
precautions. 

94.  The  Two  Main  Types  of  Suspended  Scaffolds. 
In  the  evolution  of  the  suspended  scaffold,  many  differ- 
ent methods  have  been  tried  for  supporting  the  platform 
and  for  varying  its  height  with  the  progress  of  the  work. 


FIG.  72.     ILLUSTRATING  THE   FLEXIBILITY  OF  THE    SUSPENDED 

SCAFFOLD. 


174  SUSPENDED  SCAFFOLDS 

These  have  been  repeatedly  modified  as  the  result  of 
increasing  experience  and  thought,  until  at  the  present 
time  there  may  be  said  to  be  two  standard  types,  to 
one  or  the  other  of  which  most  of  the  modern  approved 
scaffolds  belong. 

Wire  cables  are  commonly  considered  to  be  superior 
to  steel  straps  or  chains  as  a  means  of  suspension,  and 
the  use  of  cables  is  now  so  nearly  universal  that  we 
shall  give  only  passing  attention  to  other  methods  of 
support. 

In  the  forms  that  use  steel  cables  for  the  suspen- 
sion, the  platform  is  usually  raised  by  winding  up  the 
cables  upon  drums  that  are  provided  for  the  purpose, 
and  the  mechanism,  consisting  of  the  drums  and  their 
attachments  and  auxiliary  appliances,  by  which  each 
cable  or  pair  of  cables  is  wound  up,  is  called  a  "scaf- 
fold machine",  or  simply  a  "machine". 

The  two  main  types  of  suspended  scaffolds,  to 
which  we  have  referred,  differ  from  each  other  mainly 
in  the  location  of  the  machines  by  which  the  suspension 
cables  are  wound  up,  and  in  the  means  by  which  these 
machines  are  operated. 

In  one  of  them,  which  we  shall  call  the  "platform 
type",  the  drums  and  their  attachments  are  secured 
to  the  platform  itself,  and  move  with  it  when  it  is 
raised.  These  "platform  machines"  wind  up  the  sus- 
pension cables  at  their  lower  ends,  and  are  operated 
from  the  platform  by  means  of  levers  or  cranks. 

In  the  other  form  of  machine,  which  we  shall  call 
the  "overhead  type",  the  drums  and  their  attachments 
are  located  high  overhead,  at  the  points  where  the 
suspension  ropes  are  secured  to  the  steel  framework 
of  the  building.  These  "overhead  machines"  wind 


THE  TWO  MAIN  TYPES 


175 


FIG.  73.     THE  "SALT  LAKE"  SCAFFOLD  MACHINE. 

(An  early  type,  now  superseded  by  safer  forms.      Note  the  light  and  poorly-designed  pawl 
upon  which  the  men  must  rely  for  safety,  in  the  particular  machine  here  shown.) 

up  the  cables  at  their  upper  ends,  and  are  operated 
from  the  platform  by  means  of  endless  manila  ropes 
that  run  over  pulleys  or  sheaves  connected  with  the 
drums,  and  hang  down  freely  to  the  lowest  level  that 
the  platform  will  occupy  in  the  course  of  the  work. 

Although  all  scaffold  machines  that  use  wire -cable 
suspension  can  be  classed  as  either  "platform  machines" 
or  "overhead  machines",  according  as  the  cables  are 
wound  up  at  their  lower  or  upper  ends,  it  is  hardly 
necessary  to  say  that  the  details  of  design  and  construc- 
tion vary  more  or  less  among  the  various  makers  of 
such  machines.  It  would  be  impracticable,  in  a  volume 
of  this  size,  to  discuss,  minutely,  all  the  points  of  each 
make  of  machine.  It  appears  to  be  wiser  to  give  a  full 
treatment  of  some  one  form  of  each  of  the  two  main 
types ;  and  for  this  purpose  we  shall  select  the  particular 


176      SUSPENDED  SCAFFOLDS— PLATFORM  TYPE 

machines  to  which,  as  "preferred  devices  of  utility 
which  best  conserve  human  life  and  limb",  a  committee 
of  the  American  Museum  of  Safety  awarded  the 
Scientific  American  gold  medal  in  1910.  There  is 
sufficient  similarity  among  the  different  makes  of 
cable-suspended  scaffold  machines,  however,  to  insure 
a  good  understanding  of  the  safe  handling  of  all,  when 
the  special  forms  that  we  are  about  to  discuss  are  once 
thoroughly  comprehended. 

95.  Order  of  Treatment.     We  shall  discuss  the 
platform  type  of  machine  first,  and  then  the  overhead 
type.     There    are    many    considerations    that    apply 
equally  to  both,  however,  and  to  avoid  unnecessary 
repetition  we  shall  discuss  these  common  features  in 
a  third  section,  after  treating  of  the  distinctive  points 
that  characterize  each  type  of  machine  individually. 
Further  counsel,  of  a  general  nature,  will  also  be  found 
in  Section  XIII. 

PLATFORM  TYPE  OF  SCAFFOLD  MACHINE 

96.  Introductory.     In  the  platform  type  of  ma- 
chine the   drums  upon  which  the  suspension   cables 
are  wound  up  are  located  at  the  platform  and  are  se- 
cured to  it,  as  already  stated.     They  are  arranged  in 
pairs,   the   respective   drums  of  each   pair  being   set 
opposite  each  other,  one  at  the  outer  edge  of  the  plat- 
form, and  the  other  at  the  inner  edge.     Each  drum 
works  independently  of  all  the  others,   so  that  the 
platform  may  be  raised  or  lowered  at  any  of  its  points 
of  suspension,  without  being  disturbed  at  any  other 
place. 

97.  Description  of  the  Machine.     The  drums  of  the 
machines  here  described  are  31/2  inches  in  diameter 


DESCRIPTION  OF  THE  MACHINE  177 

and  71/2  inches  long,  and  are  set  with  their  axes  cross- 
wise of  the  platform  (that  is,  at  right  angles  to  the  wall 
that  is  being  laid).  At  each  end  of  each  drum,  and 
rigidly  connected  to  it,  there  is  a  ratchet-wheel  and  pawl, 
the  pawls  being  provided  with  stout  springs  to  keep 
them  always  in  position,  whether  they  are  pressing 
against  the  teeth  of  the  wheels  or  entered  into  the 
spaces  between  these  teeth. 

One  of  the  ratchet-wheels,  with  its  pawl,  serves 
simply  to  check  the  motion  of  the  drum,  and  to  prevent 
the  cable  from  unwinding  and  the  platform  from  fall- 
ing, while  the  scaffold  is  in  use  and  the  machines 
are  not  being  operated.  The  pawl  of  this  wheel  is 
secured  to  the  main  frame  of  the  machine. 

The  pawl  of  the  second  ratchet-wheel  is  used  for 
turning  the  drum  and  thereby  raising  the  platform, 
and  for  this  purpose  it  is  mounted  upon  a  short  lever 
that  swings  about  the  axis  of  the  drum  as  a  center. 
To  raise  the  platform  of  the  scaffold  the  lever  is  pushed 
down  by  the  workmen  with  the  aid  of  an  extension 
handle  some  18  inches  long,  to  give  a  greater  purchase 
than  the  lever  itself  would  directly  afford.  By  each 
downward  stroke  of  the  operating  lever  the  drum  is 
caused  to  revolve  by  a  few  teeth,  and  the  cable  is 
wound  up  by  a  corresponding  amount.  When  the 
lever  is  released,  the  pawl  at  the  opposite  end  of  the 
drum  engages  its  ratchet  and  holds  the  drum  stationary 
in  its  new  position.  The  lever  handle  can  then  be 
raised  freely,  and  by  repeating  this  process  a  suitable 
number  of  times  at  each  machine,  the  platform  can  be 
raised  by  any  desired  amount.  An  idle,  grooved  pulley 
or  sheave,  mounted  upon  a  round  horizontal  rod  that 
passes  over  the  drum  (and  parallel  to  it)  from  one  side 


178 


SUSPENDED  SCAFFOLDS— PLATFORM  TYPE 


of  the  frame  of  the  machine  to  the  other,  acts  as  a  guide 
for  the  cable,  and  moves  freely  back  and  forth  upon  its 
rod  or  axle  as  the  cable  winds  up  on  the  drum. 


FIG.  74.     THE  ''PATENT"  SCAFFOLD  MACHINE — PLATFORM  TYPE. 

(This  is  the  form  -of  machine  used  at  the  outer  edge  of  the  platform.     For  the  significance 
of  the  letters  see  paragraph  130.) 


BREAKAGE  OF  PAWL  OR  RATCHET 


179 


98.  Effect  of  the  Breakage  of  a  Pawl  or  a  Ratchet- 
wheel.  By  examining  the  construction  of  one  of  these 
machines  it  will  be  seen  that  if  either  of  the  pawls  should 
break,  the  other  one  is  quite  competent  to  hold  the 
drum  and  prevent  it  from  revolving.  The  operating 
lever,  by  means  of  which  the  cable  is  wound  up  on  the 
drum,  is  placed  on  that  side  of  the  ratchet-wheel  which 
would  move  upward  if  the  cable  were  to  unwind. 


FIG.  75. 


THE  "PATENT"  SCAFFOLD  MACHINE — PLATFORM  TYPE, 

(This  form  is  used  at  the  inner  edge  of  the  platform.) 


180      SUSPENDED  SCAFFOLDS— PLATFORM  TYPE 

Hence  if  the  fixed  pawl  should  break,  the  operating 
lever  would  fly  against  the  horizontal  cross-bar  that 
carries  the  idle  pulley  at  the  top  of  the  machine,  and 
would  thereafter  serve  to  hold  the  machine  and  prevent 
further  rotation. 

99.  Position   of   the   Operating    Lever    while    at 
Rest.     The  lever  arm,  after  it  has  been  used  to  elevate 
the  scaffold,  should  be  raised  so  as  to  stand  in  a  nearly 
vertical  position,  and  should  be  left  near  the  cross-bar 
at  the  top.     It  is  best  to  leave  the  operating  lever  as 
nearly  upright  as  possible  when  it  is  not  in  use,  as 
shown  in  the  foreground  of  Fig.  76,  not  only  because 
it  is  then  out  of  the  way,   but  also  because  if  the 
fixed  pawl   should   break,   the   one   that   is  attached 
to  the  lever  then  becomes  effective  at  once.     If  the 
lever  arm  were  left  horizontal,  or  at  any  considerable 
distance  from  the  cross-bar  or  rod  that  would  check 
its  rotation  in  the  event  of  breakage  of  the  fixed  pawl, 
it  would  be  thrown  violently  against  its  stop  by  the 
weight  of  the  platform,  and  the  shock  so  experienced 
might  fracture  some  part  of  the  mechanism. 

100.  Possibility    of    Disengaging    Both  Pawls  at 
Once.     It  might  be  thought  that  there  is  danger  of 
the  men  getting  both  of  the  pawls  out  of  mesh  with 
their  wheels  at  the  same  time,  so  as  to  allow  the  cable 
to  unwind  freely  from  the  drum,  and  the  platform  to 
fall.     This  hazard  is  not  a  real  one,  however,  for  it  is 
almost  impossible  to  get  both  pawls  out  of  mesh  at 
once,  and  the  thing  certainly  could  not  be  done  by 
accident,   nor  in   any  way  except    by    taking    very 
special  pains  to  bring  about  this  particular  state  of 
things.     The  shape  of  the  teeth  on  the  ratchet-wheel 
is  such  tha.t  neither  pawl  can  be  thrown  out  of  mesh 


DISENGAGEMENT  OF  BOTH  PAWLS 


181 


FIG.  76.     SCAFFOLD  PLATFORM,  WITH  PLATFORM-TYPE  MACHINES. 

(There  should  be  a  foot-board  and  a  side  screen  of  wire  netting  along  the  outer  margin  of 
this  platform.     See  paragraph  130.) 


182      SUSPENDED  SCAFFOLDS— PLATFORM  TYPE 

while  it  exerts  any  sensible  pressure  against  its  wheel. 
Before  the  fixed  pawl  can  be  thrown  out,  the  drum 
must  be  backed  away  from  it  by  pushing  down  the 
operating  lever;  and  when  the  lever  is  thus  depressed, 
the  full  load  comes  upon  the  movable  pawl,  which  is 
thereby  held  firmly  in  place  in  the  teeth  of  its  wheel. 
In  fact,  the  full  load  must  always  come  upon  one  or  the 
other  of  the  two  pawls,  and  so  one  or  the  other  of  them 
is  always  held  in  place,  practically  immovably.  It 
would  be  hard  to  throw  them  both  out  at  the  same  time, 
with  any  weight  on  the  platform,  even  if  a  man  were 
to  undertake  the  task  purposely  and  deliberately. 

101.  Thrust-outs,  or  Projecting  Beams,  for  Sus- 
taining the  Scaffold.  The  cables  by  which  the  scaffold 
is  suspended  are  attached,  overhead,  to  horizontal 
beams  called  "thrust-outs"  or  "outriggers",  which  are 
secured  to  the  steel  framework  of  the  building,  and 
project  outward  over  the  scaffold.  These  thrust -outs 
are  usually  steel  I-beams,  not  less  than  6  inches  in 
depth,  and  long  enough  to  project  at  least  a  foot  or  two 
beyond  the  outer  edge  of  the  platform  that  is  to  hang 
from  them,  and  also  to  extend  into  the  building  to  a 
distance  considerably  greater  than  that  by  which  they 
project  out  of  it  into  the  air.  Each  thrust -out  should 
rest  solidly  upon  one  of  the  horizontal  steel  beams  that 
are  to  form  part  of  the  outside  wall  of  the  completed 
structure,  or,  if  it  is  necessary  to  raise  the  thrust -out 
somewhat  in  order  to  leave  room  for  laying  the  floor 
arches,  it  should  be  securely  blocked  up  so  that  its 
point  of  main  support  will  come  directly  over  this 
beam.  The  end  of  the  thrust-out  that  lies  within  the 
building  should  also  be  securely  fastened  or  anchored, 
to  some  other  steel  beam  of  the  framework.  If  the 


THE  ANCHOR  BOLTS 


183 


thrust -outs  are  of  proper  length  the  part  that  lies  inside 
of  the  building  will  weigh  much  more  than  the  part  out- 
side, and  in  this  case  the  weight  of  the  beam  affords 
a  considerable  degree  of  security  to  the  scaffold,  so  far 
as  concerns  the  bodily  overturning  of  the  thrust-outs 
about  their  outer  points  of  support.  No  reliance  should 
be  placed  upon  this  element  of  safety,  however,  and  the 
inner  end  of  the  beam  should  always  be  secured  as 
solidly  as  it  would  have  to  be  if  the  beam  itself  had 
no  weight  at  all. 

102.  Anchor  Bolts.  The  end  of  the  thrust-out 
that  is  within  the  building  is  usually  made  fast  by 
means  of  a  special  U-shaped  anchor  bolt  that  is  threaded 
along  each  leg  for  a  short  distance  and  provided  with 
stout,  well -fitting  nuts,  and  with  a  plentiful  supply  of 
thimbles  consisting  of  short  sections  of  pipe,  just  a 
little  larger  than  the  stock  of  which  the  U  is  composed. 
The  inner  end  of  the  thrust -out  being  laid  across  the 


•^•ANCHOR    BOLT 


FIG.  77.     SHOWING  THE  ANCHORING  OF  THE  THRUST-OUT^ 


184  SUSPENDED  SCAFFOLDS -PLATFORM  TYPE 

beam  to  which  it  is  to  be  secured,  the  U-bolt  is  put 
in  position  in  such  a  way  that  it  surrounds  both  the 
thrust -out  and  the  beam  to  which  this  is  to  be  made 
fast.  A  yoke  is  next  slipped  over  the  ends  of  the  U, 
the  interval  between  this  yoke  and  the  threads  near 
the  ends  of  the  U  is  filled  up  with  thimbles,  and,  finally, 
the  nuts  are  fitted  to  the  threads  on  the  U  and  screwed 
up  tightly.  Jam  nuts  are  sometimes  used  on  these 
bolts,  but  they  are  seldom  necessary. 

The  depth  of  the  fixed  beams  to  which  the  thrust- 
outs  are  to  be  secured  varies  greatly,  and  therefore 
the  legs  of  the  U -bolts  are  made  considerably  longer 
than  ordinary  service  would  require.  This  construction 
is  disadvantageous  from  certain  points  of  view,  because 
it  is  often  necessary  to  interpose,  between  each  nut 
and  the  yoke  that  it  secures,  a  very  considerable  number 
of  thimbles,  through  which  the  entire  stress  that  comes 
upon  the  fastening  must  be  transmitted.  So  far  as 
simplicity  is  concerned,  it  would  be  better  to  thread 
the  U-bolts  over  a  considerable  fraction  of  the  length 
of  each  leg,  so  that  whatever  the  heights  of  the  beams 
to  be  joined  might  be,  the  nuts  could  be  screwed  down 
directly  and  solidly  against  the  yokes  themselves. 
But  it  would  be  hard  to  protect  so  great  a  length  of 
thread,  and  prevent  it  from  becoming  jammed  or 
otherwise  damaged  during  transportation,  or  while 
the  thrust -out  is  being  set  in  place,  or  in  consequence 
of  some  minor  accident  that  may  befall  it  while  the 
building  is  being  erected.  If  a  thread  should  become 
thus  bruised  or  jammed,  the  usefulness  of  the  U  would 
be  impaired  or  destroyed ;  and  it  is  mainly  for  this  reason 
that  the  legs  are  threaded  for  only  a  few  inches  near 
their  ends. 


USE  OF  BEAM  CLAMPS 


185 


103.  Use  of  Beam  Clamps.  It  sometimes  happens, 
on  account  of  lack  of  space  or  for  some  other  reason, 
that  the  standard  U-bolt  cannot  be  used  in  the  way 
we  have  described,  for  fastening  a  thrust -out  in  place. 
In  such  cases  it  is  customary  to  employ  a  clamp  which 
grips  the  flanges  of  the  thrust-out,  or  of  the  I-beam 
to  which  it  is  secured.  In  its  common  form,  this 
clamp  consists  of  two  similar  and  equal  pieces,  which 
are  shaped  so  as  to  fit  snugly  over  the  flanges  of  the 
beam  on  opposite  sides  of  the  web,  and  are  held  together 
by  a  stout  bolt.  A  hole  is  drilled  through  the  free 


FIG.  78.     A  BEAM  CLAMP. 


186      SUSPENDED  SCAFFOLDS— PLATFORM  TYPE 

(or  projecting)  extremity  of  the  clamp,  to  receive  a 
U-bolt  or  some  other  device,  to  which  the  load  that 
comes  upon  the  clamp  is  to  be  transferred. 

In  many  cases  where  a  clamp  must  be  employed, 
it  is  sufficient  to  use  it  in  connection  with  a  U-bolt, 
as  just  suggested, — the  clamp  extending  into  some  space 
or  other  that  is  too  narrow  to  admit  the  U.  Cases  of 
this  kind  arise  most  frequently  in  making  repairs  or 
alterations  upon  buildings  that  are  already  standing. 
To  attach  the  thrust-out  to  the  steel  skeleton  of  the 
building  it  is  then  often  necessary  to  cut  away  some 
part  of  the  brickwork  or  of  the  roof,  and  the  use  of  the 
beam  clamp  makes  it  possible  to  obtain  a  satisfactory 
anchorage  for  the  thrust-out  with  a  minimum  amount 
of  damage  to  the  building. 

Where  the  conditions  are  such  that  entire  reliance 
must  be  placed  upon  clamps  at  some  point,  because 
there  is  not  enough  space  for  a  U-bolt  to  be  used  for 
any  part  of  the  connection,  the  thrust-out  may  be  held 
by  one  clamp  and  the  steel  frame  of  the  building  by 
another,  the  two  clamps  being  connected  by  some 
adequate  and  safe  means  that  will  naturally  vary  with 
the  conditions.  A  safe  and  satisfactory  connection 
may  be  formed  by  using  a  pair  of  stout  steel  straps,  set 
parallel  to  each  other  and  extending  from  one  clamp 
to  the  other.  The  free  end  of  each  clamp  is  to  be 
included  between  the  steel  straps,  these  being  drilled 
at  proper  points,  near  their  ends,  so  that  a  stout  bolt 
can  be  passed  through  them  and  through  the  hole  that 
is  always  provided  in  the  clamp.  Care  should  be  taken, 
in  drilling  the  straps,  to  have  the  bolt  holes  come  in  the 
proper  places.  Furthermore,  the  point  of  attachment 
to  the  framework  of  the  building  should  be  so  chosen 


SECURING  THE  CABLES  TO  THE  THRUST-OUTS 


187 


that  the  stress  on  the  straps  will  be  sure  to  be  a  tension 
(or  pull) ,  and  so  that  they  can  never  be  put  in  compres- 
sion, under  any  circumstances. 

104.  Securing  the  Suspension  Cables  to  the  Thrust- 
outs.  In  this  form  of  scaffold  the  suspension  cables, 
at  their  upper  ends,  are  secured  to  the  thrust-outs 
by  means  of  wrought -steel  shackles.  Each  shackle  is 
rectangular  in  general  form,  and  is  made  by  bending 
a  strip  of  steel  plate  into  such  a  shape  that  it  will  fit 
over  the  outrigger,  or  thrust-out.  The  free  ends  of  the 
strip  forming  the  shackle  are  brought  near  together, 
and  project  downward  and  parallel  to  each  other, 
from  the  lower  side  of  the  thrust-out.  They  are  drilled 
to  receive  a  bolt,  from  which  the  suspension  cable 
hangs. 


FIG.  79.     ATTACHMENT  OF  THE  CABLE  TO  THE  THRUST-OUT. 


188      SUSPENDED  SCAFFOLDS— PLATFORM  TYPE 

The  cable,  at  its  upper  end,  terminates  in  a  spliced 
loop,  in  which  a  steel  eye  is  inserted.  It  is  highly  im- 
portant that  the  splicing  should  be  well  done,  and  this 
part  of  the  work  should  never  be  attempted  by  anyone 
but  a  man  especially  skilled  in  work  of  that  nature. 
In  practice,  the  splicing  and  the  insertion  of  the  steel 
eye  are  almost  always  done  at  the  factory  where  the 
cable  is  made. 

The  eye  of  the  cable  is  placed  between  the  two 
downwardly -projecting  ends  of  the  shackle,  and  the 
bolt  is  slipped  through  the  shackle  and  the  eye,  and 
fastened  securely  by  a  nut.  It  is  essential  that  the  nut 
should  fit  the  bolt  well  and  snugly,  so  that  there  shall 
be  no  possibility  of  its  working  loose  from  any  cause, 
while  the  scaffold  is  in  use.  It  is  advisable  to  use  a  jam 
nut  as  an  extra  precaution  in  this  respect. 

The  shackle  to  which  the  cable  is  secured  is  not 
usually  fastened  to  the  thrust-out  in  any  way.  The 
load  being  vertical  and  the  thrust-out  horizontal,  and 
there  being  very  little  vibration  in  the  cable  or  the 
thrust-out,  there  is  no  recognizable  tendency  for  the 
shackle  to  slip  either  inward  or  outward.  Moreover, 
on  some  buildings  in  which  there  are  projections  at 
various  heights,  it  may  be  desirable  to  shift  the  shackles 
upon  the  thrust-outs  from  time  to  time,  to  permit  the 
scaffold  to  hang  properly  while  its  platform  is  passing 
these  projections.  As  a  precaution  against  the  acci- 
dental displacement  of  the  shackle  from  some  unfore- 
seen cause,  however,  we  strongly  recommend  that  a 
hole  be  drilled  horizontally  through  the  web  of  the 
thrust-out,  near  its  outer  end,  and  that  a  bolt  be  set 
in  this  hole,  long  enough  to  prevent  the  passage  of  the 
shackle  over  the  end  of  the  thrust -out.  The  bolt 


SECURING  THE  CABLES  TO  THE  MACHINES  189 

should  be  provided  with  a  tightly -fitting  nut,  so  that 
it  cannot  drop  out,  and  it  may  be  left  lying  loosely 
in  its  hole,  although  a  better  job  may  be  had  by  fitting 
it,  at  each  end,  with  a  thimble  made  of  a  piece  of  pipe 
of  such  length  that  when  the  nut  is  screwed  tightly 
home,  the  bolt  projects  about  equally  on  both  sides 
of  the  web. 

105.  Securing  the  Suspension  Cables  to  the  Mach- 
ines. In  most  of  the  machines  of  the  type  here  con- 
sidered, the  wire  suspension  cable  is  made  fast  to  the 
machine  by  means  of  a  joint  made  with  melted  babbitt ; 
but  in  some  few  of  them  the  end  of  the  rope  is  merely 
passed  through  a  hole  of  suitable  size,  located  in  some 
part  of  the  drum  or  in  some  part  of  one  of  the  wheels 
that  are  attached  to  the  drum,  and  then  secured  by 
means  of  a  clip  of  the  Crosby  type. 

When  the  babbitted  fastening  is  used,  there  is  a  boss 
cast  upon  a  spoke  of  one  of  the  ratchet-wheels,  or  upon 
the  web  that  stretches  between  two  consecutive  spokes, 
and  through  it  a  hole  is  drilled,  parallel  to  the  axis  of 
the  machine,  and  at  the  same  distance  from  the  axis 
of  the  machine  as  the  curved  face  of  the  drum  upon 
which  the  cable  is  to  be  wound  up.  The  hole  in  the  boss 
is  a  little  larger  than  the  diameter  of  the  cable,  and  it  is 
recessed  somewhat  at  the  end  away  from  the  drum. 
The  cable  is  "seized"  or  bound  around  with  small 
wire  a  short  distance  from  its  free  end,  to  prevent  its 
strands  from  unwinding  during  the  subsequent  opera- 
tions, and  it  is  then  thrust  through  the  opening  in  the 
boss  so  that  its  extremity,  after  passing  through  the 
smallest  part  of  the  hole,  projects  into  the  recessed  space. 
Finally,  the  individual  wires  at  the  end  of  the  rope  are 
separated  and  parted,  and  the  whole  is  fixed  solidly 


190      SUSPENDED  SCAFFOLDS— PLATFORM  TYPE 

in  place  with  melted  babbitt,  as  described  in  further 
detail  in  paragraph  125. 

106.  The  Putlogs  and  Platform.     In  this  form  of 
scaffold  the  putlogs  upon  which  the  planks  of  the  scaf- 
fold rest  are  each  made  of  two  angle -irons.     These  run 
at  right  angles  to  the  face  of  the  building,  and  they  are 
bolted  to  the  scaffold  machines  at  the  inner  and  outer 
edges  of  the  platform.     They  are  made  long  enough 
to  support  six  nine-inch  planks,  this  being  the  usual 
width  of  builders'  planks  in  many  cities. 

The  horizontal  distance  from  one  putlog  to  the 
next  (or,  which  is  the  same  thing,  from  one  of  the 
overhead  thrust-outs  to  the  next)  is  limited  by  various 
considerations,  and  it  should  never  exceed  10  feet. 
It  will  often  be  less  than  10  feet,  in  places,  because  it  is 
not  always  possible  to  space  the  thrust-outs  at  uniform 
10-foot  intervals.  A  more  detailed  consideration  of 
the  platforms  of  swinging  scaffolds  is  given  in  para- 
graph 126,  where  the  features  common  to  the  two 
main  types  of  such  scaffolds  are  considered  together. 

107.  Safeguard  by  the  Pinching  of  the  Platform 
Planks.     As  will  be  plain  from  an  examination  of  the 
illustrations,  the  axis  of  the  drum  of  the  form  of  ma- 
chine we  are  now  considering  runs  crosswise  of  the 
platform,  and  the  two  upright  sides  of  the  frame  that 
supports  the  drum,   and  between  which  it  revolves, 
are  far  enough  apart  to  admit  one  ordinary  9 -inch 
platform  plank  between  them.     This  is  a  feature  well 
worth  consideration,  so  far  as  safety  is  concerned,  be- 
cause it  affords  more  or  less  protection  against  the  fall 
of  the  platform,  in  case  a  cable  should  break  or  one  of 
the  machines  should  give  way.     By  way  of  illustration, 
let  us  suppose  that  the  machines  are  spaced  10  feet 


PINCHING  OF  THE  PLATFORM  PLANKS  191 

apart,  and  that  the  platform  planks  are  14  feet  in  length, 
so  that  the  two  planks  that  meet  at  some  one  machine, 
and  pass  through  the  frame  of  that  machine,  overlap 
each  other  by  a  distance  of  four  feet.  If,  now,  one 
of  the  cables  should  break  anywhere  except  at  the 
extreme  end  of  the  platform,  the  corresponding  machine 
would  drop  until  the  ends  of  the  two  planks  that 
pass  through  it  became  pinched  between  the  putlog  and 
the  lower  teeth  of  the  ratchet-wheels  of  the  machine.  If 
the  platform  is  not  too  heavily  loaded  it  might  remain 
caught  in  this  position  until  measures  could  be  taken 
to  restore  it  to  its  proper  state.  The  scaffold  has  a 
considerable  amount  of  strength  in  the  position 
described,  and  although  no  reliance  should  be  placed 
upon  the  platform  being  caught  and  held  by  the  pinch- 
ing of  its  planks  in  the  machine,  yet  the  design  which 
makes  this  action  possible  certainly  does  afford  an  addi- 
tional safeguard  which  is  not  to  be  wholly  disregarded, 
since  it  might  result  in  saving  the  lives  of  many  men 
in  event  of  the  failure  of  a  cable.  It  has  been  claimed 
that  a  scaffold  not  too  heavily  loaded  will  remain 
suspended  by  the  pinching  action  of  the  planks,  with 
three  consecutive  pairs  of  supporting  ropes  entirely 
cut  away ;  but  we  have  not  seen  the  experiment  tried. 
If  one  of  the  cables  should  break  while  the  other  one 
that  runs  to  the  same  putlog  remains  sound  and  in  posi- 
tion, the  scaffold  will  drop  on  one  side  only;  and  even 
though  it  should  not  fall  bodily,  it  would  neverthe- 
less be  likely  to  tip  over  far  enough  to  throw  the  work- 
men to  the  ground,  if  no  proper  means  were  provi- 
ded to  prevent  them  from  plunging  over  the  edge  of 
the  platform.  If  an  inside  rope  should  break,  the  men 
would  probably  be  saved  by  the  wall  of  the  building ; 


192      SUSPENDED  SCAFFOLDS— PLATFORM  TYPE 

and  if  an  outside  one  should  break,  they  might  be  saved 
by  the  guard-rail  and  netting  which  should  always 
be  provided  along  the  outer  edge  of  the  platform. 
(Data  respecting  these  rails  and  nettings  are  given  in 
paragraph  130.) 

108.  Installing  the  Machines.  In  installing  these 
machines  the  thrust-outs  from  which  they  are  to  be 
suspended  are  first  set  up,  as  described  above,  on  the 
steel  framework  of  the  building.  The  height  at  which 
they  are  placed  depends  partly  upon  the  height  the 
finished  building  is  to  have,  and  partly  upon  the  length 
of  the  cables  on  the  machines.  At  the  outset,  the 
height  of  the  thrust -outs  does  not  ordinarily  exceed 
100  feet,  because  it  is  considered  better,  when  the  build- 
ing is  to  be  higher  than  this,  to  shift  the  thrust-outs 
during  the  progress  of  the  work  rather  than  to  use 
cables  of  greater  length  on  the  machines. 

The  thrust-outs  being  in  position,  a  line  is  passed 
down  to  the  ground  from  each  of  them,  and  made  fast 
to  the  end  of  the  cable  on  one  of  the  machines.  The 
line  from  above  is  then  drawn  up,  the  cable  on  the  drum 
of  the  machine  being  allowed  to  run  off  at  the  same  time, 
and  the  eyelet  end  of  the  rope  is  thus  raised  to  the 
thrust -out,  where  it  is  secured  to  its  shackle  by  means 
of  a  bolt,  as  already  described.  The  same  process  is 
repeated  with  each  cable,  until,  finally,  every  one  of  the 
thrust -outs  has  two  cables  attached  to  it, — one  to 
support  the  inner  end  of  a  putlog,  and  the  other  to 
support  its  outer  end. 

The  machines  are  then  placed  in  position,  -directly 
under  their  respective  thrust-outs,  and  the  planks  are 
laid  upon  the  putlogs.  Finally,  the  guard-rails  are 
put  in  place,  and  also  the  foot -boards,  wire  netting, 


DISMANTLING  THE  SCAFFOLD  193 

and  any  other  devices  that  may  be  adopted  for  the 
safety  of  the  workmen.  (See  paragraphs  130  to  135.) 

In  laying  the  platform  planks,  care  should  be  taken 
to  have  all  of  the  suspension  cables  as  nearly  vertical 
as  possible.  This  is  not  particularly  important  while 
the  scaffold  is  still  at  a  great  distance  from  the  thrust- 
out,  but  any  error  in  verticality  that  there  may  be  at 
the  beginning  of  the  work  becomes  greatly  increased 
as  the  platform  is  wound  up  toward  the  thrust-outs, 
and  when  the  suspension  cable  becomes  very  short 
it  may  hang  at  a  bad  angle  if  care  is  not  given  to  its 
proper  adjustment  at  the  outset. 

The  outriggers  or  thrust-outs  should  project  from 
the  building  at  least  18  inches  or  two  feet  beyond 
the  outer  ropes,  so  that  in  case  of  any  slight  shifting 
of  the  shackles,  either  by  accident  or  by  design,  there 
will  be  no  danger  of  their  slipping  off  over  the  ends  of 
the  thrust -outs.  This  is  important  in  all  cases,  and  it 
is  particularly  so  if  the  stop-bolt  shown  in  Fig.  79  has 
not  been  provided. 

109.  Dismantling  the  Scaffold.  In  taking  down 
a  scaffold  of  this  type  the  platform  could  be  lowered 
to  the  ground,  and  the  whole  apparatus  dismantled 
by  reversing  the  process  by  which  it  was  first 
erected.  It  is  seldom  done  this  way,  however,  unless 
the  scaffold  has  been  used  for  washing  down  the  walls 
after  they  were  completed,  and  the  cables  have  thereby 
been  unwound  again.  If  no  washing  is  done,  the 
work  will  end  with  the  cables  wound  up  on  the  drums, 
and  it  will  be  easiest  to  dismantle  the  scaffold  in  its 
highest  position.  In  that  case  the  guard-rails,  foot- 
boards, wire  netting,  and  other  safeguards  are  first 
taken  off,  and  these  and  the  planks  of  the  platform 


194     SUSPENDED  SCAFFOLDS— OVERHEAD  TYPE 

are  passed  into  the  building.  The  putlogs  are  then 
removed  from  the  machines,  and  the  drums  are  thereby 
left  hanging,  one  from  each  of  the  thrust -out  shackles. 
These  are  next  taken  in,  the  thrust -outs  are  disconnected 
from  the  steel  framework,  and  the  entire  dismantled 
scaffold  is  sent  down  on  the  elevator  that  has  been  used 
for  hoisting  the  building  material. 

110.  Miscellaneous   Safety  Features.     The  hand- 
rails, foot -boards,  and  wire  netting  that  are  recommend- 
ed for  use  in  connection  with  the  platforms  of  swinging 
scaffolds  are  considered  in  paragraph  130.     Reference 
may   also  be  made  to  paragraphs   71    to   73,   which 
treat  of  the  corresponding  features  of  pole  scaffolds. 

OVERHEAD  TYPE  OF  SCAFFOLD  MACHINE 

111.  General  Remarks.     In  this  type  of  scaffold 
there  is  no  mechanism  at  the  level  of  the  platform. 
The  machines  that  wind  up  the  supporting  cables  are 
mounted  upon  the  thrust-outs  from  which  the  platform 
is  suspended,  and  they  are  operated  by  means  of  endless 
ropes  of  hemp  or  other  vegetable  fiber,  which  pass  over 
driving  pulleys  or  sheaves  at  the  machines,  and  hang 
down  freely  by  the  side  of  the  platform,  where  they 
can  be  easily  reached  and  manipulated  by  the  workmen. 

112.  The  Thrust-outs.     The  outrigger,  or  thrust- 
out,  that  is  used  in  connection  with  the  overhead  type 
of  machine  consists  of  a  pair  of  channel  beams,  which 
are  set  parallel  to  each  other,   and  project  outward 
from  the  face  of  the  building  in  the  same  way  as  the 
single  I-beam  that  has  already  been  described  in  con- 
nection with  the  platform  type.     The  channel  beams 
should  be  7  inches  deep,  and  should  weigh  about  93/4 


THE  THRUST-OUTS 


195 


pounds  to  the  foot.  They  are  set  with  their  flanges 
turned  outward,  and  are  held  together  at  each  end  by  a 
3/4 -inch  bolt  which  passes  through  the  central  line  (or 
neutral  axis)  of  the  web  of  each  beam.  Thimbles  made 
of  iron  pipe  are  slipped  over  these  bolts  so  as  to  keep 
the  channel  beams  at  a  distance  of  1 5  inches  from  each 
other,  in  the  clear. 

The  channel  beams  that  are  used  should  be  straight, 
and  in  good  condition  in  all  respects.  The  thrust-outs 
that  they  constitute  are  to  be  firmly  secured  to  the 
steel  framework  of  the  building  by  U-bolts,  yokes,  and 


FIG.  80.    SHOWING  THE  METHOD  OF  SPACING  THE  CHANNEL  IRONS. 

nuts,  as  already  described  in  connection  with  the  I-beam 
thrust -outs  that  are  used  with  platform-type  machines. 
It  sometimes  happens  that  the  thrust-outs  of 
scaffold  machines  cannot  be  secured  to  the  building 
by  any  of  the  methods  that  have  been  described, 
and  in  such  cases  it  must  be  left  to  the  ingenuity  of  the 
man  who  is  erecting  the  scaffold  to  devise  some  method 
of  securing  them  that  will  be  both  feasible  and  safe. 
One  such  method  is  shown  in  Fig.  81,  where  the 
thrust-out  shown  on  the  right-hand  side  of  the  engrav- 


196 


SUSPENDED  SCAFFOLDS— OVERHEAD  TYPE 


FIG.  81.     SHOWING  A  SPECIAL  METHOD  FOR  SECURING  THE 
THRUST-OUT  OF  AN  OVERHEAD  MACHINE. 

(One  of  the  various  artifices  that  may  be  adopted  when  the  usual  or  typical  method, 
by  the  use  oi  U-shaped  anchor  bolts,  cannot  be  used  advantageously.) 


DESCRIPTION  OF  MACHINES 


197 


ing  could  not  be  secured  to  the  floor  beams  in  the 
usual  way,  without  weakening  the  floor  arches  by 
making  holes  through  them.  In  this  case  the  thrust- 
out  was  made  fast  by  wedging  it  down  with  a  pair  of 
wooden  uprights  that  were  held  solidly  in  position 
against  the  floor  above  by  means  of  wedges  that  were 
nailed  in  place  after  driving.  The  uprights  were  also  se- 
cured by  cross-bracing,  as  shown  in  the  illustration. 

113.  Description  of  Machines.  The  drums  and 
other  working  parts  of  each  machine  are  mounted  upon 
a  frame  that  is  built  up  of  angle-iron,  bolted  together. 
This  frame  fits  into  the  space  between  the  channel 
beams,  and  is  not  fastened  to  them,  but  is  left  free  so 
that  it  can  be  slid  back  and  forth  to  a  limited  extent 
as  the  exigencies  of  the  building  operations  may  require. 
There  is  no  danger  of  the  machine  becoming  so  far 
displaced,  outwardly,  as  to  fall  off  from  the  projecting 
end  of  the  thrust-out,  because  the  cables  that  support 


FIG.  82.     AN  OVERHEAD-TYPE  MACHINE. 


198      SUSPENDED  SCAFFOLDS— OVERHEAD  TYPE 

the  platform  of  the  scaffold  pass  down  inside  of  the 
bolt  that  unites  the  channel  beams  of  the  thrust-out 
at  their  outer  ends,  and  this  would  prevent  more  than  a 
limited  displacement  of  the  machine. 

Two  suspension  cables  run  up  to  each  machine, 
one  from  the  inside  edge  of  the  platform  and  the  other 
from  the  outside  edge,  and  a  separate  drum  is  provided 
for  each  of  them.  Each  of  the  drums  is  secured  to  a 
toothed  wheel  in  which  a  worm  engages,  and  also  with 
a  ratchet-wheel  which  is  not  used  in  the  regular  opera- 
tion of  the  machine,  but  which  is  provided  with  a  pawl 
that  can  be  dropped  into  place  when  desired.  (The 
purpose  of  the  pawl  and  ratchet  is  explained  in  para- 
graph 116.) 

The  worms  that  drive  the  two  drums  of  the  machine 
are  mounted  upon  the  same  shaft,  and  are  secured  to 
it  with  pins,  so  that  when  the  shaft  revolves  the  drums 
are  both  caused  to  turn  also,  and  the  two  suspension 
cables  that  run  to  the  platform  are  wound  up  simulta- 
neously. The  driving  shaft  runs  parallel  to  the  thrust- 
outs  by  which  the  machine  is  supported,  and  at  its 
outer  end  it  carries  a  grooved  pulley  or  sheave,  over 
which,  as  already  explained  in  paragraph  94,  there 
hangs  an  endless  rope  (known  as  the  "hand-rope"),  by 
means  of  which  the  workmen  operate  the  machine  from 
the  platform  below. 

The  suspension  cables  are  wound  around  the  drums 
in  such  a  way  that  they  hang  down,  in  every  case,  from 
the  side  of  the  drum  that  is  furthest  from  the  middle 
point  of  the  machine,  this  arrangement  having  several 
advantages.  It  renders  the  machine  much  more  com- 
pact than  it  would  otherwise  be,  and  it  also  has  certain 
safety  features  that  will  be  considered  presently. 


DISTRIBUTION  OF  STRESS  IN  THE  MACHINE  199 

It  is  plain  that  the  two  drums  of  any  given  machine 
must  revolve  in  opposite  directions  when  winding  up 
the  suspension  cables,  and  hence  one  of  the  driving 
worms  (together  with  the  gear  that  it  engages)  must 
be  right-handed,  and  the  other  one  left-handed. 

114.  Distribution  of  Stress  in  the  Machine.  The 
drums  being  located  above  the  general  framework  of 
the  machine,  it  will  be  seen  that  the  vertical  stress 
that  comes  upon  the  cast-iron  standards  that  support 
these  drums  is  compressive,  and  therefore  not  likely 
to  lead  to  rupture. 

From  the  fact  that  the  winding  drums  revolve  in 
opposite  directions,  it  will  also  be  seen  that  the  end- 
wise stress  on  the  shaft  that  carries  the  worms  is 
balanced,  because  one  drum  tends  to  pull  this  shaft  in 
one  direction,  while  the  other  one  tends  to  pull  it  in 
the  opposite  direction. 

One  important  point  to  which  attention  should  be 
given  in  connection  with  machines  of  the  overhead  type, 
is  the  equalization  of  the  load  upon  the  two  channel 
beams  that  together  constitute  the  thrust-out.  Either 
one  of  these  beams  should  be  strong  enough  to  bear, 
alone,  the  entire  load  that  comes  on  both  of  the  cables; 
but  it  is  much  better  to  equalize  the  strain  so  that 
each  of  the  channel  beams  will  carry  its  own  fair  share. 
To  accomplish  this,  care  should  be  taken  to  start  the 
cables  so  that  whenever  a  complete  layer  has  been  wound 
up  on  one  of  the  drums,  a  similar  complete  layer  will 
have  been  wound  up  on  the  other  one  at  the  same  time, 
and  in  such  a  way  that  when  one  of  the  dependent  cables 
is  near  to  one  of  the  channel  beams,  the  other  dependent 
cable  will  also  be  near  to  the  other  channel  beam  at  the 
same  time.  As  the  winding  or  unwinding  proceeds,  the 


200  SUSPENDED  SCAFFOLDS— OVERHEAD  TYPE 

tendency  will  then  be  for  the  two  tangent  points,  at 
which  the  cables  leave  their  respective  drums,  to  move 
back  and  forth  symmetrically,  so  as  to  be  always  on 
opposite  sides  of  the  center  line  of  the  machine  and 
always  at  equal  distances  from  it.  In  this  way  the 
loads  that  are  thrown  on  the  two  channel  beams  are 
equalized;  and  although  the  bending  moments,  generally 
speaking,  will  not  be  identically  the  same  on  both  beams 
at  any  one  given  instant,  yet  the  maximum  values  that 
these  bending  moments  can  have  will  be  the  same  for 
both  of  them,  if  the  ideal  conditions  that  have  been 
assumed  to  exist  are  actually  realized.  It  is  not  pos- 
sible for  these  conditions  to  be  realized  absolutely, 
and  at  times  it  may  happen  that  they  are  not  even 
roughly  approximated;  but  careful  attention  should 
nevertheless  be  paid  to  arranging  the  cables  as  in- 
dicated, because  when  this  is  done  the  tendency  toward 
equalization  of  the  stress  in  the  channel  beams  will, 
in  most  cases,  be  quite  marked. 

There  is  no  stress  on  the  hand-rope  by  which  the 
machine  is  operated,  save  that  which  is  due  to  its  own 
weight  and  to  the  pull  of  the  operators.  In  a  properly 
designed  machine,  kept  in  good  condition  in  all  respects, 
a  man  can  easily  work  the  hand-rope  with  one  hand, 
unless  there  is  a  heavy  load  on  the  platform. 

115.  Effect  of  the  Failure  of  a  Worm-pin,  by  Shear- 
ing or  Otherwise.  It  will  be  noticed  that  since  the 
cables  are  wound  so  that  the  free  (or  dependent)  end 
of  each  leaves  its  drum  on  the  side  that  is  furthest 
from  the  other  drum,  the  stress  between  the  drums  and 
the  worms  tends  to  force  the  worms  apart.  The  worms 
are  secured  to  their  shaft  by  means  of  pins  which  are 
5/16  in.  in  diameter  or  thereabouts,  and  which  are 


RIDING  OF  THE  CABLES  ON  THE  DRUMS  201 

fitted  with  smaller  split -pins  at  their  ends.  While 
reliance  must  be  placed  upon  the  worm -pins  for  holding 
the  load  under  ordinary  circumstances,  it  is  to  be  ob- 
served that  these  pins  are  by  no  means  essential  to  the 
safety  of  the  platform.  If  one  of  them  should  shear 
off,  the  worms  would  simply  be  thrown  against  the  end 
supports  of  their  shaft.  There  is  a  space  of  only  about 
one  inch,  at  either  end,  between  the  worm  and  its  sup- 
port ;  and  in  the  event  of  a  pin-failure,  each  worm,  when 
it  had  come  to  rest  in  contact  with  the  support  against 
which  it  would  be  thrown,  would  still  be  safely  in  mesh 
with  its  gear,  and  no  fall  of  the  scaffold  could  occur  un- 
less the  supports  of  the  worm -shaft  should  break,  in  ad- 
dition to  the  shearing  of  the  pin. 

116.  Riding  of  the  Cables  on  the  Drums.  In  the 
platform  type  of  machine  every  cable  is  operated  sepa- 
rately and  individually,  and  for  this  reason  the  platform 
can  be  kept  level  at  all  times,  if  it  is  so  desired.  In  the 
overhead  type,  however,  the  case  is  different.  In  oper- 
ating the  overhead  machine  by  means  of  the  endless 
hand-rope  the  two  drums  of  each  machine  always 
revolve  through  the  same  amount  or  angle.  If  the 
suspension  cables  wind  up  in  an  ideal  and  perfect  way, 
the  platform,  so  far  as  tipping  in  a  direction  perpen- 
dicular to  the  face  of  the  building  is  concerned,  will 
always  remain  level,  if  it  were  level  at  the  start.  But  it 
sometimes  happens  that  the  cables  do  not  wind  up  as 
they  should,  and  then  the  level  of  the  platform  may 
be  seriously  affected. 

One  of  the  cables,  for  example,  may  refuse  to  wind 
steadily  across  the  whole  length  of  the  drum,  but  may 
begin  to  return  before  the  end  is  reached,  by  "riding" 
back  upon  the  layer  that  has  been  only  partially  com- 


202      SUSPENDED  SCAFFOLDS— OVERHEAD  TYPE 

pleted.  This  is  equivalent  to  making  one  of  the  drums 
larger  than  the  other,  and  as  the  platform  continues 
to  be  raised  under  these  circumstances,  one  side  of  it 
is  wound  up  faster  than  the  other,  so  that  it  presently 
tips  to  an  inconvenient  degree.  Moreover,  when  a  cable 
"rides"  in  a  certain  way  it  may  occasionally  snap 
back  again  toward  the  correct  position,  and  thereby 
subject  the  whole  structure  to  a  jar  that  it  should 
never  receive. 

The  "riding"  can  sometimes  be  remedied  by 
merely  reversing  the  hand-rope  until  the  platform 
has  been  lowered  to  a  point  at  which  the  cables  are  in 
proper  condition  on  their  drums.  If  the  platform  is 


FIG.  83.     ILLUSTRATING  THE  "RIDING"  OF  THE  CABLES. 

(Note  the  condition  of  the  cable  on  the  further  drum.) 


RIDING  OF  THE  CABLES  ON  THE  DRUMS  203 

then  raised  again,  it  may  go  up  in  the  right  way,  with 
the  cables  lying  smoothly  on  both  drums. 

When  this  simple  expedient  does  not  suffice  to 
correct  the  trouble,  it  is  necessary  to  proceed  in  the 
following  manner.  A  man  first  crawls  out  upon  the 
thrust-out  at  the  top  of  the  building,  and  on  the  drum 
that  has  wound  up  the  platform  too  far  he  throws  the 
pawl  so  that  it  engages  in  its  ratchet,  and  thereby 
prevents  this  drum  from  turning  backward  in  the  sub- 
sequent operations.  The  scaffold  is  then  lowered  a 
trifle,  by  reversing  the  endless  hand-rope,  until  the  pawl 
that  has  been  thrown  in  is  set  up  solidly  against  the  next 
tooth  of  the  ratchet.  The  pawl  that  has  been  thrown 
in  will  then  be  holding  the  entire  load  that  comes 
upon  its  drum,  and  there  will  be  no  thrust  between 
the  corresponding  worm  and  its  driving  wheel.  The 
pin  securing  this  worm  to  its  shaft  is  then  removed, 
so  that  the  shaft  can  turn  freely  while  the  worm  remains 
stationary.  It  is  to  be  noted  that  the  worm -pin  can 
hardly  be  removed  while  the  gear  of  the  drum  bears 
against  the  worm  with  the  usual  force  that  is  exerted 
between  the  two  under  running  conditions,  because 
when  there  is  any  considerable  thrust  at  this  point 
the  friction  of  the  pin  against  its  hole  is  very  great. 

The  worm-pin  having  been  removed  from  the  worm 
that  engages  the  drum  that  has  wound  up  its  cable  too 
far,  the  next  step  is  to  pull  on  the  hand-rope  in  the 
direction  that  corresponds,  normally,  to  the  raising  of 
the  platform.  The  drum  carrying  the  cable  that  is  too 
high  will  not  be  affected,  because  its  worm  is  dis- 
connected from  the  driving  shaft ;  but  the  other  drum 
will  be  made  to  revolve,  and  as  a  result  the  low  side 
of  the  platform  will  be  raised,  while  the  high  side  remains 


204     SUSPENDED  SCAFFOLDS— OVERHEAD  TYPE 

stationary.  When  the  platform  has  been  made  level 
by  this  means,  the  worm  that  has  been  disconnected  is 
again  secured  to  the  driving  shaft  by  the  insertion  of  its 
pin,  and  the  pin  itself  is  made  safe  by  the  insertion  of  the 
smaller  split -pin.  The  whole  platform  is  then  raised 
sufficiently  to  permit  the  attendant  to  throw  out  the  pawl 
that  has  held  one  of  the  drums  stationary  during  this 
operation,  and  the  scaffold  is  once  more  ready  for  use. 

117.  Precautions  to  be  Observed  in  the  Foregoing 
Operation.  The  operation  described  above,  for  adjust- 
ing a  platform  that  has  been  thrown  out  of  level  by  the 
riding  of  one  of  its  cables,  is  at  best  a  delicate  one,  and 
it  must  be  performed  with  judgment,  and  only  by 
skilled  and  careful  men.  It  is  best  to  have  it  performed 
by  some  representative  of  the  company  that  owns  the 
scaffold,  rather  than  by  a  man  in  the  employ  of  the 
contractor  who  is  using  it,  because  by  so  doing  there 
is  greater  certainty  of  the  work  being  done  properly. 
The  owners  of  these  scaffolds  are  always  ready  to  give 
assistance  in  this  way,  and  in  the  leasing  of  the  scaffold 
machines  they  often  insist  upon  being  allowed  to  make 
this  adjustment,  as  one  of  the  .conditions  of  the  rental; 
but  when  the  scaffold  is  at  such  a  distance  from  the 
nearest  representative  of  the  owners  that  the  builders 
would  be  put  to  great  inconvenience  by  the  delay  in- 
volved in  sending  for  a  specially -trained  man,  it  becomes 
almost  necessary  to  have  the  adjustment  made  by  one 
of  the  employees  of  the  contractor  who  is  erecting  the 
building.  In  this  case  we  must  once  more  emphasize 
the  importance  of  having  the  adjustment  intrusted 
only  to  intelligent  men,  who  understand  the  machine 
thoroughly,  and  who  are  well  aware  of  the  paramount 
importance  of  doing  the  work  carefully  and  properly. 


PRECAUTIONS  TO  BE  OBSERVED  205 

In  adjusting  a  machine  the  cables  of  which  tend  to 
ride  improperly,  it  is  common  to  turn  the  disconnected 
worm  toward  the  center  of  the  machine  by  hand,  after  the 
pawl  is  in  place  and  the  hand-rope  has  been  backed  until 
the  strain  between  the  worm  and  its  wheel  has  disap- 
peared. This  procedure  is  often  recommended  even  by 
those  who  are  intimately  familiar  with  this  type  of  scaf- 
fold machine,  and  its  object  is  to  throw  the  worm  entirely 
out  of  mesh  with  its  wheel.  Throwing  the  worm  out  in 
this  manner  is  not  at  all  necessary,  and  it  is  in  fact 
to  be  strongly  discountenanced  because  it  introduces 
a  new  and  totally  unnecessary  source  of  danger.  The 
worm  should  be  left  in  place  after  it  has  been  dis- 
connected from  its  driving  shaft  by  the  removal 
of  the  pin,  because  it  does  not  interfere  with  making 
the  adjustment,  and  if  it  remains  in  mesh  with  its 
wheel  it  may  be  the  means  of  preventing  a  serious 
accident  in  the  event  of  the  failure  of  the  pawl,  or 
of  the  ratchet-wheel  that  the  pawl  engages. 

It  is  of  the  greatest  importance  to  see  that  the 
pawl  actually  enters  its  ratchet-wheel  to  the  full  depth 
of  the  tooth,  when  the  platform  is  to  be  leveled;  for  if 
it  rests  only  against  the  corner  of  a  tooth,  either  because 
the  tooth  is  filled  with  dirt  or  for  any  other  reason,  the 
pawl  may  spring  out  of  mesh,  or  the  end  of  the  ratchet- 
tooth  may  break  off  under  the  strain.  But  if  the  worm 
is  left  in  mesh  with  its  wheel  after  the  removal  of  the  pin, 
then  in  case  of  the  failure  of  either  the  pawl  or  the 
ratchet,  the  gear  of  the  drum  will  simply  cause  the  worm 
to  slip  along  the  shaft  for  a  distance  of  an  inch  or  two, 
until  it  brings  up  against  the  end  support  of  the  driving 
shaft,  as  explained  in  paragraph  115,  and  any  further 
rotation  of  the  drum  will  then  be  prevented. 


206     SUSPENDED  SCAFFOLDS— OVERHEAD  TYPE 

Fig.  84  illustrates  an  accident  that  occurred  in 
consequence  of  the  improper  handling  of  a  scaffold 
machine  by  an  unauthorized  person  who  did  not 
understand  the  correct  way  to  manipulate  it  in  leveling 
the  platform.  The  photograph  was  taken  immediately 
after  the  accident,  and  the  machine  is  supposed  to  be 
in  the  exact  condition  in  which  the  accident  left  it. 
The  cable  on  the  drum  that  is  now  empty  had  begun 
to  ride  improperly  from  the  very  outset,  and  the 
watchman  on  the  job,  noticing  this,  attempted  to 
remedy  the  trouble  and  have  the  scaffold  ready  for 
the  men  when  they  came  to  work  at  eight  o'clock  in 
the  morning.  He  first  crawled  out  upon  the  outrigger 
and  disconnected  the  worm  that  operated  the  drum 
that  was  at  fault,  working  it  back  into  the  position 
where  the  photograph  shows  it,  near  the  middle  of 
the  machine.  He  evidently  did  not  throw  the  pawl 
securely  into  mesh  with  its  ratchet-wheel.  He  next 
went  below  for  some  reason,  and  according  to  the  best 
evidence  available  he  jumped  down  upon  the  plat- 
form, from  a  small  height,  at  a  point  immediately 
under  the  machine.  As  the  pawl  had  not  been  properly 
meshed  with  its  ratchet-wheel,  the  shock  caused  by 
the  man's  jump  let  the  scaffold  down,  which  would 
have  been  impossible  if  the  worm  had  not  been  incor- 
rectly disconnected  from  its  gear.  When  the  cable  had 
unwound  to  its  full  length  the  end  was  no  doubt  pulled 
out  of  the  socket  to  which  it  was  attached,  or  broken 
off  close  to  the  socket.  The  man  fell  a  considerable 
distance  and  was  killed. 

118.  Insertion  of  the  Worm-pin.  Attention 
should  be  given  to  the  fact  that  although  the  worm-pins 
on  these  machines  will  always  fit  when  the  worm  is  in 


INSERTION  OF  THE  WORM  PIN 


207 


one  position,  they  may  not  do  so  when  the  worm  is 
turned  half-way  around.  The  worm  is  commonly  made 
of  cast  iron,  and  the  shaft  to  which  it  is  secured  is 
made  of  steel.  In  drilling  the  hole  for  the  worm -pin 
the  worm  is  set  in  place  upon  its  shaft,  and  the  drill 
is  passed  through  both  the  worm  and  the  shaft,  in  one 
operation.  This  insures  a  true,  fair  hole  for  the  pin,  so 
long  as  the  worm  has  the  same  position  on  the  shaft 
that  it  occupied  when  the  hole  was  first  drilled.  In 
making  the  hole,  however,  it  is  hard  to  drill  through  the 
exact  center  line  of  the  worm  and  the  shaft ;  and  more- 


FIG.  84.     ILLUSTRATING  THE  IMPROPER  HANDLING  OF  AN  OVER- 
HEAD MACHINE. 

(See  paragraph  117.) 


208  SUSPENDED  SCAFFOLDS— OVERHEAD  TYPE 

over,  the  drill,  when  it  strikes  the  steel  shaft  after  pene- 
trating the  first  thickness  of  the  worm,  is  likely  to  be 
deflected  to  a  slight  extent  so  that  when  the  job  is  com- 
pleted the  pin  will  fit  nicely  with  the  worm  in  its 
original  position,  but  will  not  pass  through  the  hole, 
properly  and  freely,  if  the  worm  is  revolved  on  the 
shaft  through  half  a  turn.  This  fact  is  often  overlooked 
by  those  operating  overhead  scaffold  machines,  and  the 
result  is  that  worm -pins,  after  they  have  been  removed 
for  adjusting  the  drums  in  leveling  the  platform  as 
described  above,  are  sometimes  hammered  violently 
in  an  attempt  to  drive  them  through  with  the  worm  in 
the  wrong  position.  The  pins  may  be  badly  damaged 
by  this  rough  treatment,  and  it  doubtless  happens, 
occasionally,  that  they  are  left  only  part  way  through, 
because  it  seems  impossible  to  get  them  to  go  in  proper- 
ly. The  remedy,  in  case  of  an  apparent  misfit  of  this 
kind,  is  very  simple,  and  consists  in  merely  bringing 
the  holes  fair  by  revolving  the  worm-shaft  through 
half  a  turn,  before  trying  to  secure  the  loose  worm  in 
place  with  its  pin.  It  would  be  well  to  mark  each 
worm  and  its  shaft  with  a  prick  punch  or  otherwise, 
so  that  there  may  be  no  uncertainty  as  to  which  way 
the  worm  should  stand  on  the  shaft,  when  it  is  ready 
to  receive  its  pin. 

119.  Attachment  of  the  Suspension  Cables  to  the 
Drums.  The  drums  upon  which  the  ropes  are  wound 
are  hollow,  and  the  cables  are  usually  secured  to  them 
as  follows.  Two  holes  are  made,  opposite  each  other, 
in  the  cylindrical  surface  of  the  drum,  one  (which  fits 
the  cable)  being  1/2  inch  in  diameter  and  the  other 
1  1/2  inches  or  thereabouts.  The  cable  is  passed 
through  the  half -inch  hole  first,  and  is  then  carried 


PUTLOGS  AND  PLATFORM  209 

straight  on  through  the  drum,  so  that  it  comes  out 
again  through  the  1  1/2 -inch  hole.  The  projecting 
end  is  next  put  through  a  kind  of  iron  collar  that  is 
technically  known  as  a  "reducer",  and  is  secured  to 
it  by  pouring  in  melted  babbitt  metal  as  described  in 
paragraph  125.  When  this  has  been  done  the  cable  is 
pulled  back  through  the  11/2  -inch  hole  until  the  iron  col- 
lar, or  reducer,  to  which  its  end  has  been  secured  rests 
against  the  inner  side  of  the  drum,  at  the  half -inch  hole. 

120.  The  Putlogs  and  the  Platform.  In  the  over- 
head type  of  scaffold  machine  the  platform  planks  are 
supported  by  putlogs,  each  of  which  consists  of  a  pair 
of  angle -irons  bolted  together,  with  thimbles  between 
to  keep  them  at  a  distance  of  about  one  inch.  The 
lower  ends  of  the  suspension  cables  are  fitted  with 
eyes  that  are  spliced  into  the  rope,  as  described  in 
paragraph  104  in  connection  with  the  upper  ends  of  the 
cables  in  machines  of  the  platform  type.  These  eyes 
are  placed  between  the  angle -irons  that  form  the  putlogs, 
and  the  lower  end  of  each  suspension  cable  is  secured 
by  passing  a  bolt  through  the  eye  of  the  cable  and 
through  both  of  the  putlog  angle -irons. 

The  width  of  the  platform,  and  the  general  char- 
acter of  the  planking,  are  the  same  as  already  described 
in  paragraph  106  in  connection  with  the  platform  type 
of  machine;  and  a  more  detailed  consideration  of  the 
platforms  of  swinging  scaffolds  in  general  will  be  given 
in  the  next  general  division  of  this  treatise,  wherein 
the  features  common  to  the  two  main  types  of  such 
scaffolds  are  considered  together.  (See  paragraph  126.) 

In  the  overhead  type  of  machine  there  is  no  pro- 
vision made,  ordinarily,  for  the  support  of  the  planking 
in  case  of  the  breaking  of  a  cable,  as  there  is  in  the 


210  SUSPENDED  SCAFFOLDS— OVERHEAD  TYPE 

particular  form  of  platform  machine  we  have  described ; 
but  this  feature  can  be  secured  in  any  suspended 
scaffold,  if  desired,  by  the  means  explained  in  para- 
graph 129,  below. 

121.  Installing  and  Dismantling  the  Machines. 
In  installing  the  overhead  machine,  the  channel  beams 
that  constitute  the  thrust -out  are  first  bolted  together 
and  are  then  set  in  position,  overhanging  the  wall  that 
is  to  be  built.  The  thrust-out,  thus  made  ready,  is 
next  secured  to  the  steel  framework  of  the  building  by 
means  of  U-bolts  and  yokes,  as  already  described, 
after  which  the  machine,  with  its  cables  properly  wound 
up  on  their  respective  drums,  is  laid  upon  the  thrust- 
out,  and  pushed  outward  from  the  building  until  it  is 
directly  over  the  place  where  the  platform  is  to  hang. 
Then  the  putlog  is  made  fast  to  the  cables,  and  when 
all  the  machines  are  thus  made  ready  the  planking 
is  laid  upon  the  putlogs,  and  the  hand-ropes  are  in- 
stalled, as  well  as  the  hand-rails,  foot -boards,  wire  net- 
ting, and  other  safety  auxiliaries. 

When  the  scaffold  is  to  be  taken  down  again,  the 
procedure  followed  depends  to  a  large  extent  upon 
the  height  of  the  thrust -outs  at  the  completion  of  the 
work.  If  they  are  more  than  one  cable -length  above 
the  ground,  it  is  usually  easiest  to  dismantle  the  whole 
scaffold,  planking  and  all,  at  the  highest  level,  close 
to  the  thrust -outs.  In  this  case  the  planks  and  all 
the  other  parts  may  be  sent  down  on  the  elevator  that 
was  used  for  raising  the  building  materials,  or  they 
may  be  lowered  in  any  other  convenient  manner. 
On  the  other  hand,  if  the  thrust-outs  are  not  more 
than  one  cable-length  high  when  in  their  final  position, 
it  may  be  more  convenient  to  lower  the  platform  to 


MISCELLANEOUS  SAFETY  FEATURES  211 

the  ground  and  dismantle  it  there,  removing  even  the 
putlogs,  so  as  to  leave  nothing  hanging  from  the  thrust- 
outs  but  the  suspension  cables  themselves.  These 
are  then  wound  up  on  their  respective  drums,  after 
which  the  machines  and  their  thrust-outs  are  lowered 
on  the  elevators  or  otherwise. 

To  facilitate  the  winding  up  and  unwinding  of 
the  suspension  cables,  the  shafts  or  axles  of  the  drums 
on  the  type  of  machine  here  under  consideration  are 
provided  with  square  ends,  over  which  a  handle  or 
"key"  can  be  fitted.  When  the  cables  are  to  be  raised 
or  lowered,  before  any  load  has  been  attached  to  them, 
or  after  every  load  has  been  removed,  the  pawls  of  the 
respective  drums  are  first  thrown  into  mesh  with  their 
ratchet-wheels,  the  worm-pins  are  then  removed  and 
the  worms  turned  toward  the  middle  of  the  machine 
by  hand  until  they  are  free  from  their  gears,  and  the 
drums,  thus  set  free,  are  then  operated  by  the  handle 
to  which  reference  has  already  been  made.  This  is 
much  quicker  and  easier  than  turning  the  hand-rope 
sheave  with  the  machine  in  full  gear,  but  it  should  never 
be  attempted  when  there  is  any  load  whatsoever 
hanging  from  the  cables. 

Workmen  often  manipulate  the  cables  by  turning 
the  disconnected  drums  by  grasping  them  by  their 
flanges,  instead  of  by  using  the  proper  handles.  This 
practice  should  not  be  permitted. 

122.  Miscellaneous  Safety  Features.  The  hand- 
rails, foot-boards,  and  wire  netting  that  are  advised 
in  connection  with  the  platforms  of  swinging  scaffolds 
are  considered  in  the  next  general  division  of  this  work. 
Reference  may  also  be  made,  regarding  these  points,  to 
Section  VII,  page  130,  which  treats  of  pole  scaffolds. 


212  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

FEATURES  COMMON  TO   BOTH  TYPES    OF    SUSPENDED 
SCAFFOLDS 

123.  Varied  Practice  in  the  United  States.     Prac- 
tice in  the  use  of  suspended  scaffolds  varies  somewhat  in 
different  parts  of  the  country,  but  the  main  principles 
are  the  same  everywhere,  and  the  differences    relate 
mostly  to  matters  of  detail.     In  Chicago,  for  example, 
the  standard  platform  plank  is  10  inches  wide,  instead 
of  9  inches  as  in  New  York.    In  Chicago,  too,  it  is  usual 
to  employ  heavy  wooden  beams  for  the  thrust-outs,  in 
place  of  the  steel  I-beams  or  channel  beams  that  are 
used  in  practically  all  other  places.     Other  differences 
of  this  same  minor  character  will  be  met  with  also,  when 
comparing  one  city  or  region  with  another,  but  it    is 
not  necessary  to  dwell  upon  them  further. 

124.  The  Suspension  Cables.     The  cables  that  are 
used  for  supporting  the  platforms  of  suspended   scaf- 
folds for  building  operations  should  be  made  of  steel 
wire.     They  should  be  not  less  than  half  an  inch    in 
diameter,  and  should  have  an  ultimate  tensile  strength 
of   not   less   than   five   tons.      The  builders    of  scaf- 
fold machines  mainly  recommend  and  use  galvanized 
cables,  because  these  resist  the  action  of  the  wreather 
better  than  the  plain  ungalvanized  ones.     Galvanized 
cast-steel  running  rope,  out  of  ordinary  stock,  should 
not  be  used,  however,  because  in  the  absence  of  special 
orders  to  the  contrary  galvanizing  is  done  mainly  on 
cables  that  are  not  adapted  for  running  over  sheaves 
or  drums.     The  cables  for  use  on  scaffolds  should  be 
made  of  what  is  known  as  ''standard  hoisting  rope", 
and  the  galvanizing  should  be  done  to  order. 

It  is  essential,  of  course,  that  the  cables   should 


SECURING  THE  CABLES  WITH  FUSIBLE  METAL       213 

possess  not  only  strength,  but  also  a  considerable  degree 
of  flexibility,  in  order  that  they  may  not  be  damaged 
from  being  wound  upon  the  drums.  The  likelihood  of 
injury  from  bending  is  not  nearly  so  great  in  scaffold 
machines,  however,  as  it  is  in  elevators  and  other  forms 
of  hoisting  apparatus  where  the  rope  is  being  almost 
continually  wound  up  and  unwound. 

Some  form  of  protection  against  the  action  of 
the  weather  should  be  provided  for  the  suspension 
cables.  If  they  are  galvanized,  the  coating  furnishes 
sufficient  protection  so  long  as  it  is  in  good  condition. 
When  the  cables  are  not  galvanized,  or  when  the  galvan- 
izing has  become  worn  off  in  places,  they  should  be 
treated  with  some  approved  preservative  preparation. 
The  rope  makers  furnish  special  substances  for  this 
purpose,  but  if  these  cannot  be  procured  readily,  good 
results  may  be  had  by  soaking  the  cables  with  first-class 
cylinder  oil  or  linseed  oil,  mixed  with  finely-divided 
graphite. 

The  cables  should  be  thoroughly  inspected,  from 
time  to  time,  to  see  that  they  remain  in  good  condition; 
and  if  there  is  any  question  whatsoever  about  their 
absolute  safety,  they  should  be  replaced  at  once. 

125.  Securing  the  Ends  of  the  Cables  with  Fusible 
Metals.  In  fastening  the  end  of  a  steel  cable  into  a 
recess  or  socket  by  running  in  melted  metal,  a  so-called 
"seizing  strand",  composed  of  fine  wire,  is  first  wound 
tightly  around  the  cable,  at  a  point  that  will  lie  just 
outside  of  the  recess  or  socket  when  the  job  is  complete. 
This  is  to  hold  the  strands  of  the  cable  together,  and 
prevent  them  from  fraying  during  the  subsequent 
operations.  The  cable  is  then  passed  entirely  through 
the  recess  into  which  it  is  to  be  secured,  so  as  to  project 


214  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

beyond  it  to  a  convenient  distance,  and  its  end,  beyond 
the  seizing  strand,  is  next  opened  out  so  that  each  wire 
is  separated  from  its  neighbors  until  the  whole  has  the 
appearance  of  a  sort  of  brush  with  divergent  bristles. 
The  hemp  center  of  the  cable  should  then  be  removed 
as  far  back  as  the  seizing  strand,  or  as  near  to  it  as 
practicable. 

Opinions  differ  as  to  the  best  procedure  after  this 
point  has  been  reached.  Many  users  of  wire  cables 
believe  that  each  separate  wire  should  be  turned  back 
upon  itself  so  as  to  form  a  sort  of  hook,  the  point  of 
which  should  lie,  in  every  case,  toward  the  center  of  the 
cable.  In  making  the  connection  in  this  way,  the 
hook-shaped  ends  of  the  wires  are  all  drawn  back  into 
the  socket  or  recess  to  which  the  cable  is  to  be  secured, 
and  a  tapered  pin  is  driven  lightly  into  the  middle  of  the 
brush,  to  spread  its  separated  and  incurved  wires. 
Melted  lead  or  some  other  readily  fusible  metal  is 
then  poured  into  the  recess  so  as  to  fill  it  completely, 
the  pouring  being  so  managed  that  the  molten  metal 
will  run  in  among  the  separated  wires  as  perfectly  as 
possible.  If  the  operation  here  described  is  well  done, 
a  fastening  is  obtained  that  should  be  stronger  than  the 
body  of  the  cable  itself. 

Lead  has  been  mentioned  in  the  preceding  para- 
graph as  a  material  for  filling  in  the  sockets  or  recesses 
to  which  the  ends  of  cables  are  attached,  because  it  has 
been  employed  for  this  purpose  quite  extensively  in  the 
past  and  is  still  used  to  quite  an  extent  at  the  present 
time.  In  fact,  cable  connections  that  are  made  with 
melted  metal  in  this  way  are  commonly  known  as 
"leaded  ends",  even  when  they  contain  no  lead.  The 
manufacturers  of  wire  cables  do  not  favor  the  use  of 


SECURING  THE  CABLES  WITH  FUSIBLE  METAL         215 

lead  for  making  the  ends,  nor  do  they  recommend 
bending  the  tips  of  the  separated  wires  into  hooks. 
Having  frayed  out  the  end  of  the  cable  as  described 
above,  and  spread  the  separated  wires  out  into  a  brush- 
like  shape,  they  clean  the  wires  thoroughly  with  gasolene 
and  then  fill  the  recess  with  melted  zinc. 

Zinc,  as  a  filling  material,  has  several  marked  ad- 
vantages over  lead,  when  it  is  properly  applied.  If 
the  wires  are  perfectly  clean,  the  zinc,  when  poured, 
will  adhere  to  them  firmly,  as  is  illustrated  in  the 
ordinary  process  of  galvanizing.  Zinc  also  expands 
upon  solidifying,  and  hence  it  tends  to  fill  the  spaces 
about  the  wires  and  within  the  recess,  very  solidly. 
Lead,  on  the  other  hand,  will  not  adhere  to  the  wires, 
but  merely  runs  around  them,  so  as  to  inclose  them 
without  adhesion.  It  also  contracts  upon  solidifying, 
and  therefore  tends  to  loosen  in  the  recess  and  around 
the  wires.  Moreover,  it  is  not  so  strong  or  rigid  as  zinc. 
Lead  is  easier  to  handle  than  zinc,  however,  because 
it  melts  at  a  lower  temperature,  and  (unlike  zinc)  it 
does  not  take  fire  when  melted,  nor  does  it  volatilize 
to  any  important  degree. 

Builders  of  scaffold  machines  use  babbitt  metal 
quite  extensively  in  making  so-called  ''leaded  ends" 
for  the  suspension  cables.  If  the  babbitt  metal  is  of 
good  quality  it  is  greatly  preferable  to  lead,  because  it 
is  more  rigid  and  it  penetrates  better  among  the  wires. 
Care  should  be  taken  to  use  babbitt  of  first-class  quality, 
however.  This  metal  is  often  procured,  for  use  in 
securing  the  ends  of  cables,  from  dealers  in  second-hand 
machinery  and  scrap  metal.  We  consider  that  this 
is  not  a  wise  procedure,  because  there  is  great  variation 
in  the  metal  that  is  obtained  in  this  way,  and  from  time 


216  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

to  time  the  purchaser  is  likely  to  obtain  a  markedly 
inferior  quality  that  should  not  be  used  for  securing 
the  cables.  The  total  cost  of  new  metal  for  this  pur- 
pose is  small,  and  it  is  much  better  to  use  an  alloy  that 
is  prepared  especially  for  the  purpose,  and  mixed  in 
known  proportions. 

When  making  a  zinc  end,  the  wires  of  the  cable 
are  sometimes  pickled  in  acid  in  addition  to  being 
cleaned  with  gasolene,  in  order  to  insure  as  perfect  a 
union  as  possible  between  the  two  metals.  This  is  not 
to  be  recommended  for  general  practice,  however, 
because  there  is  likelihood  of  free  acid  being  left  between 
the  wires  of  the  cable,  just  back  of  the  zinc  plug. 
Corrosion  arising  in  this  way  is  likely  to  continue  when 
the  cable  is  in  service,  long  after  the  acid  that  started 
the  action  has  become  exhausted.  If  acid  is  used,  the 
finished  end  should  be  immersed  for  a  time  in  a  solution 
of  washing  soda  or  soda  ash,  as  soon  as  it  has  become 
cool.  It  is  safer  to  rely  on  gasolene  alone,  for  the  clean- 
ing, and  to  omit  the  acid  altogether. 

After  a  cable-end  has  been  secured  by  the  use  of 
either  lead,  babbitt,  or  zinc,  it  is  of  prime  importance 
to  let  the  fused  metal  cool  slowly,  by  natural  radiation. 
It  is  a  more  or  less  common  practice  to  throw  the  heated 
end  of  the  cable,  with  its  attached  socket,  into  a  pail 
of  water,  or  to  dash  water  over  the  hot  connections  as 
a  whole,  if  the  end  has  been  made  fast  to  a  recess  in 
some  large  piece  of  metal.  This  should  be  strongly 
discountenanced,  because  the  sudden  chill  alters  the 
physical  character  of  the  heated  parts,  affecting  the 
cable  particularly,  and  making  it  likely  to  fracture  at  or 
near  the  point  where  it  enters  the  recess  into  which  it 
is  secured. 


THE  PLATFORM  217 

As  the  heat  to  which  the  end  of  the  cable  is  sub- 
jected in  making  a  so-called  "leaded  end"  destroys  any 
oil  or  grease  that  may  have  been  on  the  surface  or  be- 
tween the  strands  of  the  immediately  adjoining  part  of 
the  cable,  it  is  well  to  soak  the  end  in  oil  for  a  short 
time,  or  to  treat  it  with  some  special  form  of  dressing, 
before  it  is  put  into  service. 

126.  The  Platform.  The  planks  composing  the 
platform  should  be  laid  tightly  together,  so  that  there 
is  no  chance  for  even  a  small  implement  to  fall  down 
between  them. 


FIG.  85.     HOOK  FOR  HOLDING  THE  SCAFFOLD  NEAR  THE  WALL. 

(This  is  caught  over  a  floor  beam,  and  its  left-hand  end  is  wired  to  the  suspension 

cable.) 

The  platform  should  hang  close  to  the  building, 
so  that  there  will  not  be  room  for  a  man  to  fall  between 
it  and  the  wall.  It  is  usual  to  arrange  the  scaffold  so 
that  there  will  be  a  space  of  two  to  four  inches  between 
the  inner  edge  of  the  platform  and  the  wall  of  the  build- 
ing, and  hooks  are  often  used  to  prevent  the  platform 
from  swinging  away  from  the  wall, — these  being  caught 
over  conveniently  situated  I-beams  at  one  end,  and 
wired  to  the  suspension  cables,  near  the  level  of  the 
platform,  at  the  other  end.  To  prevent  the  platform 


218  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

from  swinging  in  too  close  to  the  building,  fenders  are 
also  provided,  consisting  of  pieces  of  plank  running 
crosswise  of  the  platform,  tacked  to  it  with  nails,  and 
projecting  inward  toward  the  building  to  a  distance 
sufficient  to  insure  the  proper  interval  between  the 
platform  and  the  wall.  In  painters'  scaffolds  the  ends 
of  the  corresponding  fenders  are  usually  fitted  with 
small  wooden  wheels,  which  roll  along  the  wall  as  the 
scaffold  is  raised;  but  the  wheels  are  omitted  from  the 
builders'  scaffold,  because  the  platform,  in  this  case, 
is  supposed  to  be  so  adjusted  that  it  will  hang  freely 
at  the  proper  distance  from  the  wall,  and  the  fenders 
are  provided  merely  to  steady  it. 

The  platform  planks  should  be  made  of  spruce 
when  this  wood  is  available,  though  first-class  long- 
leaf  southern  pine  is  also  acceptable  for  the  purpose. 
Whichever  wood  is  used,  the  planks  should  be  of  the 
quality  indicated  in  paragraph  42,  in  connection 
with  the  bricklayers'  pole  scaffold.  They  are  usually 
nine  inches  wide,  and  they  should  be  at  least  two  inches 
thick  for  all  ordinary  work,  and  correspondingly 
thicker  than  this  if  the  work  is  unusually  heavy.  The 
planks  are  ordinarily  twelve  or  fourteen  feet  in  length, 
so  that  with  the  usual  spacing  of  the  putlogs  each 
plank  will  overlap  each  putlog  by  either  one  foot  or 
two  feet.  The  platform  should  be  laid  with  special  care, 
and  the  planks  should  overlap  the  putlogs  by  the 
same  amount  at  each  end. 

The  putlogs  upon  which  the  platform  planks  rest 
should  never  be  set  further  apart  than  10  feet.  Some 
builders  separate  them  by  an  interval  as  great  as  15 
feet  when  planks  of  sufficient  length  can  be  had  for  the 
platform, — extra  thick  planks  being  used,  if  necessary, 


PASSING  MATERIALS  TO  THE  PLATFORM  219 

to  obtain  the  requisite  stiffness ;  but  the  more  conserv- 
ative and  cautious  builders  are  agreed  that  this  is  a 
mistake,  and  that  the  ten-foot  limit  for  the  distance 
between  the  putlogs  is  wisely  chosen,  and  should  not 
be  exceeded. 

127.  Passing  Materials  to  the  Platform.  The  ma- 
terials that  are  used  in  laying  a  wall  from  a  swinging 
scaffold  are  carried  up  inside  of  the  building  by  a 
temporary  elevator  or  by  some  other  form  of  hoisting 
device,  and  are  left  at  the  floor  nearest  to  the  platform 
of  the  scaffold.  When  the  platform  is  immediately 
opposite  to  a  floor,  it  is  easy  to  pass  the  materials  out 
to  it,  either  through  a  window  opening  or  over  the 
upper  edge  of  the  growing  wall;  but  as  the  scaffold  is 
drawn  up  with  the  progress  of  the  work,  it  will  presently 
reach  a  height  at  which  it  is  no  longer  easy  to  transfer 
the  material  directly  to  the  platform  of  the  scaffold, 
from  the  floor  below.  It  is  customary  to  meet  this 
condition  by  making  use  of  auxiliary  platforms  sup- 
ported upon  horses  inside  of  the  building,  these  horse 
platforms  being  commonly  used  not  only  for  passing 
materials  to  the  swinging  scaffold,  but  also  for  laying 
the  inner  courses  of  the  wall  at  the  same  time.  The 
use  of  horse  platforms  for  the  laying  of  brick  is  dis- 
cussed elsewhere  in  this  treatise,  and  in  the  present 
place  they  are  considered  merely  as  a  means  for 
delivering  supplies  to  the  outside  scaffold. 

A  single  inside  platform,  one  horse  high,  suffices 
for  the  handling  of  the  supplies  until  the  swinging 
platform  has  risen  seven  or  eight  feet  above  the  floor 
from  which  the  delivery  is  made,  but  in  erecting 
buildings  whose  stories  are  unusually  high  it  may  be 
necessary  to  use  a  two-stage  inner  platform,  one  level 


220  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

of  which  is  one  horse  high,  while  the  other  is  two  horses 
high;  and  three  such  platforms,  at  three  different 
heights,  may  be  required  in  extreme  cases.  The 
materials  may  be  passed  from  one  helper  to  another, 
from  the  floor  where  they  are  delivered  by  the  elevator 
up  to  the  highest  of  the  horse  platforms  and  then  out 
upon  the  swinging  scaffold;  or  runways  may  be  pro- 
vided, up  which  the  materials  can  be  transported  to  the 
desired  level,  by  means  of  barrows  or  hods. 

When  the  wall  of  a  building  approaches  the  floor 
above  that  from  which  the  material  has  been  recently 
delivered,  it  is  common  to  send  further  supplies  to  the 
higher  floor,  before  the  platform  of  the  scaffold  has 
quite  reached  that  level.  They  are  then  passed  down 
to  the  working  platform,  instead  of  being  raised  from 
below.  When  this  is  done,  special  care  should  be 
taken  to  deposit  the  materials  upon  the  scaffold  plat- 
form gently,  and  without  any  sensible  shock.  In 
scaffold  work  generally,  the  helpers  often  throw  loads 
down  upon  the  platform  from  their  shoulders,  thereby 
jarring  the  whole  structure  and  sometimes  damaging 
it  seriously.  In  all  cases  it  is  highly  important  to  take 
whatever  measures  may  be  necessary,  to  prevent  this 
dangerous  practice  from  being  followed.  The  general 
principle  should  always  be  borne  in  mind,  that  a  load 
falling  through  even  a  short  distance  strains  the  scaf- 
fold to  a  far  greater  extent  than  the  same  load  would, 
if  it  were  deposited  upon  the  platform  gently. 

128.  Overloading  the  Platform.  The  platform 
of  a  scaffold  should  never  be  used  for  the  storage  of 
considerable  quantities  of  material.  It  is  necessary 
to  have  a  certain  amount  on  the  platform  in  addition 
to  that  which  the  workmen  may  need  at  the  moment, 


SAFEGUARD  BY  THE  PINCHING  OF  THE  PLANKS      221 

in  order  to  avoid  the  delays  that  would  otherwise 
arise  if  the  material  were  not  supplied  with  perfect 
regularity.  It  should  never  be  allowed  to  accumulate 
sufficiently  to  subject  the  scaffold  to  a  serious  strain, 
however.  This  fundamental  principle  must  be  borne 
in  mind  with  special  care,  because  the  helpers  often 
go  right  on  delivering  materials,  even  when  the  laying 
of  brick  has  been  suspended  for  a  time.  The  whole 
operation  should  be  subjected  to  a  supervision  effective 
enough  to  prevent  the  supply  of  materials  from  more 
than  keeping  pace  with  the  quantities  that  are  used. 

129.  Safeguard  by  the  Pinching  of  the  Platform 
Planks.  This  method  of  safeguarding  is  of  secondary 
importance,  but  it  nevertheless  merits  passing  notice. 


FIG.  86.     STEEL  STRAP  FOR  INCLOSING  THE  PLATFORM  PLANKS. 

It  consists  in  providing  a  device  of  some  kind,  which, 
in  case  one  or  more  of  the  suspension  cables  should 
break,  becomes  operative  in  such  a  way  as  to  prevent 
the  fall  of  the  platform  planks  that  the  broken  cable 
was  designed  to  support. 

In  the  form  of  platform  scaffold  described  in 
Section  X,  the  framework  of  the  machine,  as  explained 
in  paragraph  107,  is  supposed  to  be  designed  so  that 
it  will  cause  certain  of  the  planks  to  bind  together  at 
their  ends  when  they  have  dropped  a  short  distance, 
and  thus  prevent  a  further  descent.  The  same  prin- 
ciple can  be  put  into  practice,  in  any  other  form  of 
builders'  suspended  scaffold,  by  slipping  over  the  ends 
of  both  courses  of  planks,  where  the  two  overlap, 


222 


SUSPENDED  SCAFFOLDS— EITHER  TYPE 


a  flat  loop  or  closed  strap  of  steel  plate,  of  the  general 
form  indicated  in  Fig.  86.  Such  a  loop  is  easily  made 
by  any  good  blacksmith.  It  should  be  about  3/8  inch 
thick  and  3  inches  wide,  and  long  enough  to  take  in 
six  9-inch  planks  easily.  Its  two  long  sides  should 


FIG.  87.     WRONG  POSITION  OF  THE  STEEL  STRAP. 

(The  strap  is  here  too  near  the  end  of  the  upper  course  of  planking.) 

be  separated  by  a  clear  space  of  (say)  41/4  inches,  so 
that  it  may  be  passed  readily  over  a  pair  of  overlapping 
2 -inch  planks.  The  wreld  in  the  strap  should  be  care- 
fully made,  and  should  be  located  somewhere  near 
the  middle  of  one  of  the  long  sides. 


FIG.  88.     CORRECT  POSITION  OF  THE  STEEL  STRAP. 

(It  should  be  located  near  the  end  of  the  lower  course  of  planking.) 

The  strap  should  not  be  placed  at  the  center  of 
the  overlap  of  the  planks,  but  should  be  shifted  to 


SAFEGUARD  BY  THE  PINCHING  OF  THE  PLANKS      223 

one  side  of  this  point,  so  as  to  take  in  the  ends  of  the 
lower  layer  of  planks  with  a  margin  of  safety  of  from 
4  to  6  inches.  It  'is  important  to  note  that  this  is 
the  most  effective  position  that  the  strap  can  have, 
and  that  it  would  be  worth  very  little  if  it  were  set  so 
as  to  just  include  the  ends  of  the  upper  planks. 

If  the  putlog  that  ordinarily  supports  the  plat- 
form at  this  point  should  fall,  leaving  the  strap  to 
sustain  the  total  load,  the  planks  would  be  subjected 
to  a  bending  stress  that  would  be  particularly  severe 
along  the  line  marked  6;  and  there  would  also  be 
a  considerable  pressure  between  the  upper  and  lower 
planks  at  their  line  of  contact,  a.  The  intensity  of 
these  stresses  would  deperd  in  considerable  measure 
upon  the  position  of  the  strap,  and  would  be  least 
when  the  strap  is  placed  as  far  away  from  a  as  possible. 
For  example,  all  the  stresses,  both  in  the  strap  and 
in  the  planks,  would  be  only  about  one-third  as  great 
if  the  strap  were  placed  as  shown  in  Fig.  88,  as  they 
would  be  if  it  were  placed  as  indicated  in  Fig.  87, 
—the  two  diagrams  being  drawn  to  the  same  scale.  It 
is  evident,  therefore,  that  under  certain  conditions 
the  platform  might  be  safely  sustained  if  arranged 
as  in  Fig.  88,  even  though  the  stresses,  with  the  dis- 
position shown  in  Fig.  87,  were  severe  enough  to  break 
the  planks  or  the  strap. 

With  the  consecutive  planks  of  the  platform  over- 
lapping each  other  by  two  feet  (that  is,  with  each 
plank  overlapping  the  putlog  by  one  foot),  a  well- 
made  strap  of  the  dimensions  suggested  above,  when 
placed  in  the  position  indicated  in  Fig.  88,  would  no 
doubt  help  to  sustain  the  planking  temporarily  in 
the  event  of  a  suspension  cable  breaking,  unless  the 


224  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

platform  were  carrying  a  load  considerably  in  excess 
of  the  limit  that  should  be  permitted.  It  is  not  in 
actual  use,  so  far  as  we  are  aware,  and  under  ordinary 
circumstances  it  is  not  needed,  because  the  scaffold 
can  be  made  quite  safe  without  it,  by  correct  installa- 
tion and  careful  inspection  followed  by  the  prompt 
and  conscientious  making  of  such  changes  and  repairs 
as  may  be  found  to  be  needed.  The  strap  is  here  sug- 
gested and  described,  however,  because  it  might  be 
advisable  to  adopt  it  in  certain  cases,  where  the  failure 
of  the  scaffold  would  be  likely  to  be  followed  by  un- 
usually serious  consequences,  either  to  the  workmen 
or  to  persons  on  the  street  below.  When  made  to 
the  dimensions  given  above,  it  should  weigh  a  little 
less  than  forty  pounds. 

130.  Guard-rails,  Foot-boards,  and  Side  Screens. 
For  preventing  the  fall  of  men,  implements,  or  material, 
suspended  scaffolds  should  be  furnished  with  pro- 
tective devices  similar  to  those  already  described  in 
connection  with  the  bricklayers'  pole  scaffold.  Each 
scaffold  should  have  a  stout  wooden  hand-rail  (or 
breast-rail),  set  at  a  height  of  about  40  inches,  and 
running  along  the  entire  length  of  the  platform,  above 
its  outer  edge.  The  rail  should  be  made  of  sound 
material,  and  be  free  from  bad  knots  and  cross- 
grained  spots.  It  should  be  securely  fastened  in  posi- 
tion, and  should  be  strong  enough  to  resist,  with  per- 
fect safety,  the  shock  caused  by  a  large  man  falling 
heavily  against  it.  Rope  is  sometimes  used  in  the  place 
of  the  wooden  railing  here  advised,  but  it  is  inferior 
from  all  points  of  view,  except  as  regards  convenience 
in  transportation  and  installation.  Even  when  the 
work  is  of  such  a  nature  that  the  platform  must  be 


GUARD-RAILS,  FOOT-BOARDS,  AND  SIDE  SCREENS      225 

drawn  up  unevenly,  rigid  wooden  rails  can  be  used 
with  entire  success  if  they  are  made  in  sections  of 
reasonable  and  convenient  length.  The  platform 
of  the  scaffold  can  bend  only  at  the  putlogs,  and 
there  is  no  need  of  any  trouble  from  lack  of  pliability 
in  the  railings  if  they  are  of  the  same  length  as  the 
planks,  and  the  successive  sections  are  joined  together 
in  some  flexible  manner,  opposite  the  suspension 
cables. 

On  a  scaffold  of  the  overhead  type,  where  the 
machines  are  located  on  the  thrust-outs  or  outriggers 
and  the  cables  move  with  the  platform,  the  hand- 
rail may  be  lashed  directly  to  the  suspension  cables. 
It  should  preferably  run  inside  of  the  cables,  so  that 
any  shock  to  which  the  rail  may  be  subjected  will  be 
resisted  by  direct  pressure  against  the  cables  them- 
selves, and  not  merely  by  the  lashings  or  other  fasten- 
ings by  which  the  rail  is  attached  to  them. 

In  a  scaffold  of  the  platform  type,  where  the 
machines  are  attached  to  the  platform  and  move  with 
it,  the  hand-rail  cannot  be  conveniently  secured  directly 
to  the  cables,  but  must  be  made  fast  to  some  other 
part  of  the  structure.  In  the  particular  form  of  plat- 
form scaffold  described  and  discussed  in  paragraph  97, 
page  176,  provision  is  made  for  the  support  of  the 
guard-rail  by  riveting  to  the  outer  support  of  the 
machine  that  is  used  at  the  outer  edge  of  the  platform 
two  perforated  ears  (A  and  B  in  Fig.  74),  through 
which  there  passes  an  upright  rod  having  at  the  top 
an  eye  (not  shown  in  the  engraving)  to  which  the 
hand-rail  can  be  lashed.  For  reasons  similar  to  those 
given  in  the  preceding  paragraph,  it  is  best  to  run 
this  rail  on  the  inner  side  of  the  iron  supports,  so  that 


226  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

any  shock  that  may  be  thrown  upon  it  will  be  trans- 
mitted to  the  supports  by  direct  pressure,  and  not  by 
means  of  tension  upon  the  fastenings. 

Along  the  outer  margin  of  the  platform  of  either 
type  of  scaffold,  and  in  close  contact  with  it,  there 
should  be  a  securely-supported  foot-board,  projecting 
at  least  7  inches  above  the  platform,  for  preventing 
tools  and  materials  from  falling  over  the  edge.  In  the 
overhead  type  of  scaffold  the  foot -board  may  be  made 
fast  to  the  suspension  cables,  and  it  should  run  inside 
of  these  cables.  In  the  particular  form  of  platform 
scaffold  that  we  have  discussed,  each  of  the  vertical 
rods  that  support  the  hand-rail  has  an  offset  near  the 
bottom  (C  in  Fig.  74),  to  hold  the  foot-board  in  place. 

In  addition  to  the  hand-rail  and  the  foot -board, 
it  is  highly  desirable  to  provide  a  side  screen  of  stout 
wire  netting,  extending  from  the  hand-rail  to  the  floor 
of  the  platform.  In  some  localities  a  screen  of  this 
kind,  or  some  equally  effective  substitute  for  it,  is 
required  by  law.  The  screen  should  have  a  mesh 
small  enough  to  prevent  objects  more  than  half  an 
inch  in  diameter  from  passing  through,  and  it  should 
be  securely  attached  to  the  hand-rail  and  also  to  the 
foot -board  (or  the  platform) ,  at  intervals  short  enough 
to  insure  its  safety  and  stability,  even  if  it  were  sub- 
jected to  a  considerable  impact  or  shock. 

The  foot-board  is  often  omitted  when  the  wire 
screen  is  used,  but  it  is  far  better  practice  to  install 
them  both, — the  screen  serving  to  prevent  the  fall  of 
men  and  large  objects  generally,  while  the  foot-board 
serves  to  retain  small  implements  and  fragments  of 
building  material.  Moreover,  it  is  not  always  easy 
to  make  a  tight  joint  between  the  wire  screen  and 


GUARD-RAILS,  FOOT-BOARDS,  AND  SIDE  SCREENS     227 


FIG.  89.     ILLUSTRATING  THE  USE  OF  WIRE  NETTING  FOR  SIDE 
SHIELDS  AND  FOR  OVERHEAD  PROTECTION. 

(See  paragraphs  130  and  134.) 


228  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

the  platform  when  no  foot-board  is  used.  When  both 
are  adopted,  it  is  preferable  to  have  the  screen  rest 
against  the  inner  side  of  the  foot-board, — that  is, 
against  the  side  that  faces  the  platform,  as  shown 
in  Fig.  89. 

At  a  corner,  where  two  platforms  come  together 
at  right  angles,  the  corresponding  guard-rails  and 
foot-boards  should  be  securely  fastened  together,  and 
the  wire  netting  should  be  passed  around  the  corner 
in  such  a  way  as  to  give  the  same  degree  of  security 
there  that  is  afforded  at  any  other  point.  If  the  sus- 
pension cables  that  are  nearest  the  corner  on  the 
outside  edges  of  the  two  platforms  are  not  too  far 
apart,  it  is  often  possible,  by  using  specially  stout  and 
long  material,  to  bring  the  ends  of  the  guard-rails 
together  and  unite  them  by  lashings,  clamps,  bolts, 
or  nails,  so  that  a  safe  and  secure  corner  can  be  formed 
without  the  aid  of  a  post;  but  if  there  is  the  slightest 
doubt  as  to  the  efficiency  of  the  corner  thus  formed, 
the  rails  should  be  supported  by  a  post,  erected  solidly 
and  effectively,  so  that  it  cannot  be  overthrown  by  any 
shock  to  which  it  is  likely  to  be  subjected.  We  especial- 
ly desire  to  emphasize  the  importance  of  bracing  this 
post  with  care,  because  it  is  almost  invariably  either 
omitted  altogether,  or  set  up  in  the  most  insecure 
manner,  so  that  it  is  practically  useless  for  the  purpose 
for  which  it  is  intended. 

The  guard-rail,  foot-board,  and  wire  screen  should 
extend  entirely  across  the  platform,  wherever  it  has 
a  free  end.  In  a  suspended  scaffold  of  the  overhead 
type,  the  guard-rail  and  foot-board,  where  they  cross 
the  platform,  can  be  made  fast  to  the  last  pair  of  sus- 
pension cables,  and  the  wire  screen  can  be  secured  to 


OVERHEAD  PROTECTION  229 

the  rail  and  to  the  foot -board,  just  as  it  is  along  the 
side  of  the  platform.  When  the  scaffold  is  of  the 
platform  type,  however,  so  that  the  suspension  cables 
cannot  be  utilized  for  the  direct  attachment  of  the 
guard-rail  or  the  foot-board,  it  may  be  necessary 
to  erect  a  post  for  this  purpose  at  the  inner  edge  of 
the  platform,  and  perhaps  also  at  the  outer  edge. 
In  such  cases  the  posts  should  receive  the  same  con- 
sideration that  is  recommended  in  the  last  paragraph, 
and  should  be  solidly  braced  and  made  capable  of 
safely  withstanding  a  heavy  shock. 

In  using  a  suspended  scaffold  it  is  all  too  common 
to  slight  the  guard-rails,  foot-boards,  and  wire  netting. 
In  many  cases  the  netting  and  the  foot -board  are 
omitted  (as  in  Fig.  76),  and  the  guard-rail  is  often 
erected  in  a  weak  and  altogether  inadequate  way, 
or  is  entirely  absent.  It  is  hardly  necessary  to  say 
that  this  is  all  wrong.  The  expense  involved  in  pro- 
viding these  safeguards  and  having  them  right  is 
trivial,  and  it  is  hard  to  see  what  sufficient  reason  a 
builder  can  give  for  failing  to  install  them,  in  a  safe 
and  substantial  way.  When  properly  constructed 
they  are  very  effective  in  saving  life  and  limb,  and 
in  many  places  they  are  also  required  by  law. 

131.  Protection  of  Scaffold  from  the  Fall  of 
Objects  from  Above.  Workers  upon  swinging  scaffolds 
are  often  left  wholly  unprotected  against  injury  from 
the  fall  of  objects  from  above.  We  are  glad  to  note, 
however,  that  builders  are  coming  to  see  the  wisdom 
of  providing  such  protection,  in  cases  in  which  there 
is  danger  from  this  source.  There  is  no  special 
difficulty  involved,  the  main  question  being  that  of 
expense. 


230  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

It  is  hardly  possible  to  arrange  a  scaffold  of  any 
kind  so  that  the  men  at  work  upon  it  will  be  protected 
from  injury  in  case  of  the  fall  of  a  heavy  mass  like  a 
beam  or  a  large  stone.  Many  accidents  occur,  however, 
from  the  fall  of  small  objects  such  as  rivets,  bricks,  or 
tools,  against  which  the  men  can  easily  be  shielded. 
Protection  against  the  fall  of  massive  objects  should  be 
insured  by  adopting  general  precautionary  measures 
in  connection  with  the  management  of  the  work  as 
a  whole,  rather  than  by  relying  upon  special  safeguards 
associated  with  the  scaffold  itself.  Beams  and  other 
heavy  masses,  for  example,  should  never  be  suspended, 
even  momentarily,  over  any  scaffold  upon  which  men 
are  at  work.  It  is  not  sufficient  to  keep  the  platform 
clear  of  workmen  immediately  under  the  beam, 
because  in  the  event  of  an  accident  through  the  failure 
of  the  hoisting  apparatus,  the  whole  scaffold  might 
be  wrecked. 

When  used  in  connection  with  a  suspended  scaffold 
of  the  overhead  type,  a  roof  or  covering  for  shielding 
the  men  from  falling  tools  or  other  small  objects  may 
be  secured  directly  to  the  cables  that  support  the  plat- 
form. This  plan  works  very  well  upon  buildings  not 
higher  than  the  length  of  the  suspension  cables  of  the 
scaffold.  It  is  less  convenient,  however,  when  the 
level  of  the  thrust -outs  has  to  be  changed  during  the 
progress  of  the  work,  because  the  suspension  cables 
must  be  disconnected  in  order  to  shift  the  machines, 
and  this  means  that  the  protective  covering  must  also 
be  temporarily  removed,  if  it  is  attached  to  the  cables 
themselves. 

132.  Canvas  Shields  over  the  Platform.  Stout 
canvas  is  sometimes  used  for  the  protective  cover, 


PROTECTIVE  SHIELDS  OF  CANVAS 


231 


FIG.  90.     SUSPENDED  SCAFFOLD  (PLATFORM  TYPE)  WITH  OVER- 
HEAD SHIELD  OF  CANVAS. 

(This  particular  shield  could  be  greatly  improved,  by  attending  to  the  suggestions   given 

in  paragraph  132.) 


232  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

though  in  many  respects  it  is  not  an  ideal  material. 
When  it  is  used  it  should  stand,  at  its  lowest  point, 
from  three  to  six  feet  (according  to  the  tension  to 
which  it  is  subjected)  above  the  heads  of  the  men  who 
are  to  be  protected;  because  an  object  falling  upon  a 
canvas  surface  may  depress  it  by  a  considerable 
amount  before  being  brought  to  rest,  and  ample 
provision  for  such  depression  should  be  made  in  fixing 
the  height.  (The  shield  shown  in  Fig.  90  is  too  low  to 
afford  full  protection.) 

The  canvas  that  is  used  should  be  quite  heavy, 
that  known  as  "No.  6  duck"  being  usually  considered 
best.  This  may  be  had  in  many  widths,  the  most 
useful  width  being  either  48  inches,  60  inches,  or  72 
inches.  It  should  be  reinforced  along  the  edges  by 
sewing  on  extra  strips  of  similar  canvas,  and  rings 
should  be  worked  in  it  at  frequent  intervals  along  each 
edge,  to  receive  the  fastening  ropes.  Grommets  will 
serve  in  the  place  of  rings,  but  they  are  not  so  good. 
Stretch  the  canvas  fairly  tight,  and  do  not  set  it  hor- 
izontally, but  incline  it  sufficiently  to  cause  it  to  shed 
water  easily,  the  outer  edge  being  the  lower.  The 
shield  should  be  made  fast  with  half -inch  hemp  rope, 
this  being  better  than  a  larger  size  because  it  will 
yield  and  stretch  more  readily  when  the  canvas  shrinks 
through  becoming  wet. 

The  edges  of  the  canvas  should  be  supported  at 
intervals  of  not  more  than  five  feet.  When  the  machine 
is  of  the  overhead  type  and  the  shield  is  secured  to  the 
suspension  cables  (which  are  commonly  10  feet  apart), 
its  edges  should  therefore  be  supported  midway  between 
the  cables.  This  may  be  effected  most  conveniently  by 
running  a  half -inch  rope  diagonally  upward  from  the 


PLANK  ROOFS  FOR  SCAFFOLD  PLATFORMS  233 

middle  point  of  each  free  edge  to  each  of  the  two 
nearest  cables,  and  making  the  ropes  fast  to  the  cables 
at  a  height  of  six  feet  or  more  above  the  canvas. 
(They  may  be  attached  while  the  cables  are  slack,— 
that  is,  before  raising  the  platform, — and  disconnected 
again  from  the  thrust -outs  overhead.) 

To  strengthen  and  stiffen  the  canvas  so  that  it 
will  be  better  able  to  resist  the  action  of  the  wind,  it  is 
advisable  to  sew  two  or  three  ropes  to  it  along  its 
entire  length.  These  should  run  lengthwise  of  the 
platform,  and  should  be  spaced  at  equal  distances 
between  the  edges  of  the  shield.  Thus  if  two  stiffening 
ropes  are  used,  one  of  them  should  be  secured  at  one- 
third  of  the  width  of  the  canvas  from  each  edge;  and 
if  three  are  used,  one  should  lie  along  the  middle  of  the 
shield,  and  the  other  two  should  come  midway  between 
this  central  rope  and  the  respective  edges. 

The  cost  of  a  properly-made  canvas  shield  is 
quite  considerable,  and  this  fact,  taken  in  connection 
with  the  difficulty  of  handling  and  supporting  such  a 
shield  and  the  admitted  fact  that  canvas  is  far  from 
ideal  in  other  respects  also,  indicates  that  under  most 
circumstances  it  is  better  to  substitute  for  it  a  protec- 
tive roof  of  wire  netting  or  of  wood,  substantially 
supported  in  whatever  way  appears  best  adapted  to 
the  type  of  the  scaffold,  and  to  the  conditions  under 
which  it  is  to  be  used. 

133.  Plank  Roofs  for  Overhead  Protection. 
When  an  overhead  protective  shield  is  desired  for  a 
suspended  scaffold  of  the  platform  type,  in  which  the 
drums  that  wind  up  the  suspension  cables  are  located 
upon  the  platform  itself,  the  support  of  the  shield 
calls  for  special  consideration.  In  a  scaffold  of  the 


234 


SUSPENDED  SCAFFOLDS— EITHER  TYPE 


overhead  type  the  suspension  cables  move  with  the 
platform,  and  the  shield  can  therefore  be  secured  to 
them,  directly  and  permanently,  without  trouble; 
but  in  the  platform  type  the  platform  moves  while 


FIG.  91.     PLATFORM-TYPE    SCAFFOLD,    WITH    OVERHEAD    PRO- 
TECTION OF  PLANKS  SUPPORTED  BY  A  SPECIAL 
STEEL  FRAMEWORK. 


DOUBLE-PLATFORM  SCAFFOLDS  235 

the  cables  remain  stationary,  and  hence  when  using 
a  scaffold  of  this  kind  the  overhead  shield  must  either 
be  shifted  on  the  cables  from  time  to  time,  or  sup- 
ported by  a  separate  framework  of  some  kind  as  in 
Fig.  91. 

In  view  of  this  difficulty  a  double  platform  is 
sometimes  used,  one  layer  of  planks  being  7  or  8  feet 
above  the  other.  (Fig.  92  illustrates  this  construction, 
although  the  particular  scaffold  there  shown  contains 
numerous  objectionable  features,  as  will  appear  from 
the  suggestions  that  follow.)  Each  plank  layer  is 
supported  by  its  own  putlogs,  the  putlogs  of  the  upper 
platform  being  set  directly  over  those  of  the  lower 
one.  The  lower  putlogs  are  suspended  individually 
from  the  upper  ones  by  means  of  separate  short  lengths 
of  cable,  which  do  not  have  to  be  disturbed,  even 
when  changing  the  positions  of  the  thrust -outs.  The 
workmen  stand  upon  the  lower  platform,  and  the 
upper  one  affords  them  the  desired  protection. 

In  using  a  double  platform  of  this  character,  the 
suspension  cables  (in  the  overhead  type  of  scaffold) 
and  the  machines  (in  the  platform  type)  should  be 
secured  to  the  upper  platform,  precisely  as  though 
this  were  the  only  platform  present.  In  other  words, 
a  suspended  scaffold  having  a  double  platform  should 
be  constructed  so  that  if  the  short  cables  supporting 
the  lower  layer  of  planking  were  cut  away,  the  remain- 
ing parts  would  constitute  a  single-platform  scaffold 
conforming  in  all  respects  to  the  construction  advised 
for  such  a  scaffold  in  this  treatise. 

Care  must  be  taken  to  have  the  fastenings  by 
which  the  lower  platform  is  hung  from  the  upper  one 
equal  in  strength,  in  every  way,  to  the  suspension  by 


236 


SUSPENDED  SCAFFOLDS— EITHER  TYPE 


which  the  upper  one  is  supported  from  the  thrust- 
outs.  It  is  recommended  that  the  short  cables  which 
join  the  two  platforms  be  provided  with  a  well-made 
spliced  eye  at  each  end.  The  bolts  that  unite  the  two 


FIG.  92.     SMALL  DOUBLE-PLATFORM  SCAFFOLD  OF  THE 
PLATFORM  TYPE. 

(Note  the  absence  of  the  guard-rail  and  wire  screen  at  the  end.     See  also  the  text.) 


DOUBLE-PLATFORM  SCAFFOLDS  237 

angle-irons  of  which  each  putlog  is  composed  can  then 
be  passed  through  these  eyes,  giving  solid  connections 
to  both  platforms.  When  the  putlogs  are  not  com- 
posed of  double  angle-irons,  or  when,  for  any  other 
reason,  the  eyes  of  the  short  cables  cannot  readily 
be  secured  to  the  putlogs  directly,  rectangular  yokes 
may  be  used  to  make  the  connection,  these  being 
slipped  over  the  putlogs,  just  as  they  are  slipped  over 
the  thrust-outs  in  attaching  the  upper  ends  of  the 
main  suspension  cables  of  a  platform-type  scaffold. 

In  the  double-platform  scaffold  the  men  work 
upon  the  lower  platform.  If  the  scaffold  is  of  the  over- 
head type,  there  will  be  no  need  of  anyone  going  out 
upon  the  upper  layer  of  planking,  except  when  it 
becomes  necessary  to  shift  the  thrust -outs  to  a  higher 
level,  in  the  course  of  the  erection  of  the  wall.  If  the 
scaffold  is  of  the  platform  type,  however,  the  men 
whose  duty  it  is  to  raise  the  scaffold  from  time  to 
time  must  go  out  upon  the  upper  platform  to  operate 
the  machines,  and  a  railing  and  foot -board  should 
therefore  be  provided  on  the  upper  platform  in  such 
cases.  Wire  netting  is  also  recommended,  though 
the  hand-rail  and  foot-board  will  ordinarily  be  quite 
sufficient  in  this  place.  Whichever  type  of  scaffold 
is  used,  it  is  important  to  see  that  the  lower  platform, 
where  the  workmen  are,  is  fitted  up  with  substantial 
guard-rails,  foot -boards,  and  wire  netting,  in  strict 
accordance  with  the  standard  that  is  described  above 
in  paragraph  130,  and  recommended  for  use  upon 
single -platform  scaffolds. 

Whenever,  in  using  a  double-platform  scaffold, 
it  becomes  necessary  for  a  man  to  pass  from  either 
of  the  platforms  to  the  other  one,  he  should  not  be 


238  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

permitted  to  climb  over  the  outer  edge  of  the  scaffold, 
nor  over  one  of  its  free  ends.  He  should  be  required 
to  use  a  ladder  placed  so  that  it  is  easily  accessible 
from  both  platforms,  or  else  to  pass  into  the  building 
from  the  platform  that  he  is  leaving,  and  out  from 
the  building  again  at  the  proper  level,  to  the  platform 
that  he  wishes  to  reach.  When  neither  of  these  methods 
is  feasible,  the  two  platforms  may  be  connected  by  a 
special  ladder,  either  entirely  inclosed  or  at  least 
provided  with  a  back -bar,  to  make  the  passage  from 
one  level  to  the  other  safe.  It  would  seldom  be  worth 
while  to  go  to  this  trouble,  however,  because  the  wire- 
netting  shield  described  in  the  next  paragraph  is  far 
cheaper,  lighter,  and  more  practical,  and  it  suffices 
for  nearly  all  conditions. 

134.  Overhead  Protection  by  Wire  Netting. 
Unless  protection  is  desired  even  against  very  small 
particles  of  material,  an  overhead  shield  of  wire 
netting,  similar  to  the  side  screens  that  were  dis- 
cussed in  paragraph  130,  is  very  effective.  A  screen 
of  stout  wire,  with  a  mesh  not  exceeding  half  an  inch 
each  way,  will  prevent  the  passage  of  almost  any 
object  that  would  be  likely  to  injure  the  workers. 
Such  a  screen  has  various  advantages.  It  weighs 
far  less  than  a  plank  covering,  and  it  is  not  seriously 
disturbed  (as  a  canvas  covering  is  likely  to  be)  by 
strong  winds.  Moreover,  it  has  the  advantage  that  it 
allows  light  to  pass  through  it  freely.  Most  of  the 
injuries  that  occur  on  suspended  scaffolds  from  the 
fall  of  materials  from  above  are  caused  by  rivets, 
bolts,  drift -pins,  or  the  various  hand  tools  that  the 
steel  men  use.  Wire  netting  is  quite  effective  in  stop- 
ping objects  of  this  kind,  if  it  is  made  of  stout  wire 


OVERHEAD  PROTECTION  BY  WIRE  NETTING 


239 


with  a  mesh  not  more  than  half  an  inch  square,  as 
already  suggested.  The  wires  of  such  a  screen  should 
be  soldered  together  at  every  crossing. 

Fig.  89  shows  an  overhead  screen  of  this  kind  in 
use  on  a  suspended  scaffold  of  the  overhead  type,  and 
Fig.  93  gives  a  different  view  of  the  same  screen.  In 
the  case  here  illustrated  horizontal  wooden  stringers 
were  run  parallel  to  the  face  of  the  building,  and 
secured  to  the  outer  and  inner  rows  of  suspension 
cables,  respectively,  at  a  height  of  about  8  feet  above 


FIG.  93.     A    SCAFFOLD    PLATFORM    WITH    AN   OVERHEAD    PRO- 
TECTION OF  WIRE  NETTING. 


240  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

the  platform.  Wooden  cross-pieces  were  then  laid 
upon  the  stringers  to  support  the  wire-mesh  screen, 
which  was  fastened  in  place  securely  enough  to  be 
safe  against  any  chance  of  displacement,  by  the  wind 
or  otherwise.  When  a  protective  screen  of  this  kind 
is  to  be  used  on  a  scaffold  of  the  platform  type,  it  is 
best  to  support  it  by  means  of  a  special  framework, 
similar  to  the  one  shown  in  Fig.  91  for  supporting  the 
plank  covering.  This  framework  can  be  held  in  posi- 
tion by  the  suspension  cables  without  being  actually 
fastened  to  them,  the  cables  being  run  through  open- 
ings in  the  framework  or  through  ears  attached  to  it, 
the  whole  being  arranged  so  that  the  framework  can 
slide  freely  along  the  cables  as  the  platform  is  raised. 

135.  One  Scaffold  Over  Another.  Two  or  more 
entirely  separate  suspended  scaffolds  are  sometimes 
employed  simultaneously  upon  the  same  job,  one  of 
them  at  a  higher  level  than  the  other.  In  cases  of  this 
kind  it  is  highly  important  to  protect  the  men  upon 
the  lower  scaffold  from  materials,  tools,  or  other 
objects  that  may  fall  from  the  upper  one.  Such  pro- 
tection may  be  had  either  by  providing  the  lower 
scaffold  with  a  protective  roof  such  as  has  been  des- 
cribed above, —  or,  still  better,  by  arranging  a  fixed 
protective  shield  or  platform  at  some  level  between 
the  two  scaffolds.  The  latter  plan  may  be  put  into 
effect  quite  easily,  when  the  scaffold  machines  are  of 
the  platform  type,  by  laying  a  flooring  of  stout  planks 
over  the  thrust -outs  from  which  the  lower  scaffold  is 
suspended.  (See  Fig.  94.)  A  flooring  of  this  kind  may 
be  made  very  effective,  so  far  as  concerns  the  pro- 
tection of  the  lower  scaffold  from  materials  (even  from 
heavy  planks)  falling  from  the  upper  one;  but  it 


ONE  SCAFFOLD  OVER  ANOTHER 


241 


FIG.  94.     Two   SCAFFOLDS   IN   USE   AT  THE   SAME   TIME,   ONE 

ABOVE    THE    OTHER. 

(The  thrust-outs  that  support  the  lower  scaffold  are  covered  with  a  layer  of  planks,    to 
protect  the  men  on  the  lower  platform.) 


242  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

should  not  be  forgotten  that  it  does  not  protect  the 
lower  scaffold  from  objects  falling  from  points  lower 
than  the  outriggers  or  thrust -outs  upon  which  the 
planking  is  laid. 

When  a  plank  floor  is  placed  upon  a  tier  of  out- 
riggers as  here  described,  care  should  be  taken  to  lay 
the  planks  securely,  and  to  see  that  they  overlap  by  a 
very  considerable  amount,  both  upon  themselves  and 
upon  the  outriggers.  Floors  of  this  kind  should  be 
examined  frequently,  and  especially  after  storms  or 
high  winds,  to  see  that  they  remain  in  safe  condition; 
and  it  is  wisest  to  lash  the  planks  to  the  outriggers, 
or  to  make  them  fast  in  some  other  effective  way, 
so  that  there  may  be  no  question  of  their  security.  The 
planks  should  always  rest  upon  the  upper  sides  of 
the  outriggers,  and  should  never  be  lashed  against 
their  under  sides. 

136.  Shifting  the  Thrust-outs.  The  suspension 
cables  upon  scaffold  machines  of  either  type  are  usually 
from  75  to  100  feet  in  length.  When  the  building  to 
be  erected  is  higher  than  the  length  of  one  cable,  the 
thrust -outs  are  first  set  at  a  height  somewhat  less  than 
the  length  of  a  cable,  and  the  scaffold  is  raised  in  the 
usual  manner,  as  the  work  progresses,  until  it  comes 
near  to  the  thrust-outs  from  which  it  is  supported. 
New  thrust -outs  are  then  placed  at  a  higher  level,  and 
the  cables  are  shifted  to  them.  When  this  has  been 
done  the  old  thrust-outs  are  removed,  and  the  work 
proceeds  as  before, — the  thrust-outs  being  shifted 
in  this  way  every  time  the  height  of  the  wall  has  in- 
creased by  approximately  one  cable  length. 

The  shift  from  one  set  of  thrust-outs  to  the  next 
should  be  made  with  special  care,  because  accidents 


SHIFTING  THE  THRUST-OUTS  243 

are  quite  likely  to  occur  in  this  part  of  the  work  unless 
it  is  superintended  by  a  person  who  understands  it 
thoroughly.  The  builders  of  scaffold  machines  often 
specify,  in  leasing  them,  that  they  shall  be  notified 
when  it  is  necessary  to  make  the  shift,  so  that  they 
can  send  trained  men  of  their  own  to  supervise  the 
work ;  and  we  strongly  advise  that  this  be  done  when- 
ever it  is  feasible.  It  is  not  necessary  to  clear  the 
platforms  of  material  while  the  change  is  being  made, 
but  the  workmen  should  be  required  to  withdraw  from 
the  sections  that  are  being  shifted,  so  that  in  case  of 
accident  the  results  will  not  be  needlessly  serious. 

In  changing  the  position  of  the  outriggers  upon 
either  type  of  scaffold,  the  new  outriggers  are  first  set 
in  place,  and  the  platform  is  then  raised  to  within  8 
or  10  feet  of  the  old  ones  and  securely  lashed  to  them, 
or  fastened  to  them  in  some  other  perfectly  safe  way, 
so  that  when  the  main  suspension  cables  are  discon- 
nected the  platform  will  still  be  supported  safely,  and 
with  no  possibility  of  a  fall.  The  drums  upon  which 
the  main  cables  are  wound  up  should  then  be  reversed 
or  backed  away  slightly,  so  as  to  throw  the  entire 
weight  of  the  scaffold  upon  the  lashings  or  other 
temporary  connections,  and  render  the  main  suspen- 
sion cables  slack.  It  is  important  that  this  slacking  - 
up  should  be  done,  and  done  carefully,  so  that  in  sub- 
sequently disconnecting  the  main  cables  there  will 
be  no  sudden  jar  or  shock  thrown  either  upon  the 
scaffold  or  upon  any  of  its  connections. 

When  the  suspension  cables  have  thus  been  ren- 
dered slack,  they  are  disconnected  from  the  putlogs 
(if  the  scaffold  is  of  the  overhead  type),  and  the 
machines  are  drawn  in  and  transferred  to  the  newly 


244  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

installed  thrust -outs  at  the  higher  level.  Their  cables  are 
then  lowered  and  again  made  fast  to  the  platform  putlogs, 
precisely  as  described  above  in  paragraph  121,  where  the 
first  installation  of  a  scaffold  of  this  type  is  discussed. 
If  the  scaffold  is  of  the  platform  type  the  procedure 
is  much  the  same,  except  in  regard  to  such  details  as 
will  readily  suggest  themselves.  When  the  platform 
has  been  made  fast  to  the  lower  thrust -outs  and  the 
drums  have  been  slowly  and  carefully  eased  back  so  as 
to  throw  the  weight  of  the  platform  upon  the  lashings 
or  other  temporary  connections  and  render  the  main 
suspension  cables  slack,  these  main  cables  are  dis- 
connected from  the  old  thrust -outs  and  drawn  up  to 
the  new  ones  above,  and  there  made  fast  in  the  usual 
manner, — as  already  described  in  paragraph  108, 
where  the  installation  of  this  type  of  machine  is  des- 
cribed. To  facilitate  the  drawing -up  of  the  suspension 
cables  of  platform-type  machines  it  is  customary  to 
fasten  the  pawls  of  the  machines  with  wire,  in  such 
a  way  that  they  will  remain  clear  of  their  ratchets 
while  the  cables  are  unwinding  from  the  drums.  This 
may  not  be  regarded  as  ideal  practice,  because  it  sug- 
gests the  possibility  of  forgetting  the  wire  on  some 
of  the  pawls,  and  attempting  to  restore  the  scaffold  to 
use  with  these  pawls  out  of  action.  An  oversight  of 
this  kind  would  not  be  likely  to  occur  in  actual  work, 
however,  because  the  temporary  lashings  could  not 
be  slacked  up,  as  described  in  the  next  paragraph, 
unless  the  pawls  were  properly  engaging  the  teeth 
of  their  ratchet-wheels;  but  if  it  should  be  considered 
undesirable  to  fasten  the  pawls  back  in  this  way  or  in 
any  other  way,  they  can  be  held  out  of  mesh  by  the 
men  while  the  cables  are  unwound  from  the  drums. 


COMPARISON  OF  SUSPENDED  SCAFFOLDS  245 

Whichever  type  of  scaffold  is  used,  the  next  step, 
after  the  connections  have  been  properly  and  safely 
made  to  the  new  thrust-outs,  is  to  raise  the  platform 
by  turning  the  drums  in  the  usual  way  until  the  load 
is  again  supported  entirely  by  the  main  cables,  and  the 
temporary  lashings  or  supports  are  slack.  The  tem- 
porary lashings  are  then  removed,  the  old  thrust-outs 
are  taken  away,  and  the  scaffold  is  ready  for  use. 

The  method  of  shifting  described  above  assumes 
that  extra  thrust -outs  are  available.  If  this  is  not  the 
case  temporary  beams  may  be  arranged  to  support 
the  scaffold  while  the  thrust-outs  are  changed.  The 
necessary  modifications  in  the  procedure  will  be 
evident  enough  without  special  description.  The 
same  precautions  should  be  observed,  in  making  the 
shift  in  this  way,  that  are  recommended,  above,  in 
connection  with  the  use  of  the  extra  thrust-outs. 
Special  care  should  also  be  taken  to  secure  the  tempor- 
ary beams  safely  and  solidly  to  the  building. 

Nobody,  save  those  who  are  necessarily  employed 
in  the  shifting  of  the  thrust -outs,  should  be  allowed 
to  go  out  upon  the  platform  until  the  old  thrust -outs 
have  been  disconnected  and  drawn  back  into  the 
building.  It  is  a  mistake,  for  example,  to  permit 
bricklayers  or  their  helpers  to  return  to  their  work 
upon  the  platform,  while  the  men  who  have  been  shift- 
ing the  scaffold  are  still  engaged  in  removing  the 
old  thrust -outs,  over  their  heads. 

137.  Comparison  of  the  Overhead  and  Platform 
Scaffolds.  The  platform  type  of  suspended  scaffold 
is  easier  to  install  than  the  overhead  type,  but  many 
builders  prefer  the  overhead  type  because  it  leaves 
the  platform  entirely  free  from  machinery  of  any 


246 


SUSPENDED  SCAFFOLDS— EITHER  TYPE 


kind,  so  that  every  square  foot  of  it  can  be  utilized 
by  the  workmen.  The  overhead  style  is  particularly 
convenient  for  use,  too,  when  it  is  necessary  to  lower 
the  scaffold  from  time  to  time,  because  it  can  be 
lowered  by  merely  reversing  the  direction  in  which  the 
hand-rope  or  driving-rope  is  pulled.  In  the  particular 
type  of  platform  machine  that  is  herein  discussed, 
however,  the  platform  can  be  lowered  only  by  raising 
the  pawls  alternately,  by  hand.  In  performing  this 
operation  the  operating  lever  of  the  machine  is  first 
depressed  sufficiently  to  bring  the  total  load  upon  its 
pawl.  The  other  pawl  is  then  held  out  of  mesh  while 
the  lever  is  eased  up  by  one  stroke,  after  which  the 


FIG.  95.     THE   "PERFECT"  SCAFFOLD  MACHINE, 


CORNICE  WORK  247 

fixed  pawl  is  allowed  to  fall  back  into  place.  The  load 
being  then  transferred  to  the  fixed  pawl,  the  lever  pawl 
is  in  turn  held  out  of  mesh,  and  the  lever  is  swung 
down  to  its  lowest  position,  its  pawl  being  thereafter 
released  and  allowed  to  re-enter  the  ratchet.  This 
entire  process  is  repeated,  again  and  again,  until 
the  platform  has  been  lowered  as  far  as  desired. 

It  should  not  be  inferred,  from  what  has  been  said, 
that  all  platform  machines  are  actuated  by  pawls  and 
ratchet-wheels.  Fig.  95,  for  example,  shows  a  form 
in  which  the  drum  is  controlled  by  a  worm.  When 
using  this  type  the  platform  can  be  reversed  and 
lowered  as  easily  as  in  the  overhead  machines,  by 
merely  reversing  the  motion  of  the  operating  handle, 
which  is  attached  to  the  worm-spindle  shown  at  A 
in  the  engraving.  A  full  discussion  of  these  points  of 
difference,  with  a  view  to  bringing  out  the  relative 
merits  and  demerits  of  the  various  designs  of  machines 
that  are  actually  made  and  available,  would  require 
a  prohibitive  space.  Moreover,  such  discussion  would 
not  be  entirely  consonant  with  the  purpose  of  this 
work,  which,  as  explained  in  the  preface,  is  merely  a 
treatise  on  the  principles  of  safety  engineering  as 
applied  to  scaffold  work,  rather  than  upon  scaffold 
work  as  a  whole;  and  to  illustrate  these  principles 
it  is  not  necessary  to  take  up  every  form  of  scaffold 
machine  in  detail. 

138.  Cornice  Work.  The  cornice  of  a  building 
sometimes  presents  troublesome  problems  when  sus- 
pended scaffolds  are  used.  This  is  particularly  the 
case  when  the  cornice  projects  outward  to  a  consider- 
able distance.  In  such  a  case  the  scaffold  may  be 
removed  before  the  cornice  is  completed,  or  small 


248  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

openings  may  be  left  in  the  cornice  for  the  suspension 
cables,  the  cables  being  drawn  out  through  these 
openings  when  the  work  has  been  completed  and  the 
scaffold  is  to  be  taken  down. 

In  erecting  a  cornice  with  the  aid  of  a  suspended 
scaffold  there  is  often  a  temptation  to  allow  too  great 
a  stress  to  be  thrown  upon  the  scaffold  platform,  not 
only  by  loading  it  improperly  with  materials  but  also 
by  lifting  heavy  objects  in  such  a  way  that  the  men 
or  the  jacks  that  are  used  for  this  purpose  rest  upon 
the  scaffold  platform,  and  so  transmit  to  it  the  weight 
of  the  object  lifted.  Special  care  should  be  taken  to 
avoid  anything  of  this  kind,  because  although  the 
scaffold  is  supposed  to  be  strong  enough  to  safely 
support  any  load  to  which  it  may  be  legitimately  sub- 
jected in  the  course  of  the  ordinary  routine  work, 
it  is  not  intended  to  sustain  the  uncertain  and  perhaps 
quite  severe  additional  stresses  that  may  be  thrown 
upon  it  in  the  ways  indicated,  or  in  other  similar 
ways  that  were  not  contemplated  by  the  designers 
of  the  scaffold. 

139.  Life  Lines  and  Safety  Belts.  The  men  who 
have  to  secure  or  shift  the  thrust-outs  for  the  support 
of  suspended  scaffolds,  and  particularly  those  who  have 
to  adjust  or  inspect  overhead  machines  or  attach  the 
upper  ends  of  the  cables  of  platform-type  machines, 
must  crawl  out  upon  the  thrust-outs  to  a  greater  or 
lesser  extent,  and  be  thereby  exposed  to  loss  of  life 
through  falling.  A  stout  life-belt  should  therefore  be 
provided  for  every  man  who  must  go  out  upon  a  thrust- 
out, — the  belt  being  securely  attached  to  a  strong, 
new  rope,  the  end  of  which  should  be  made  fast  to 
some  part  of  the  framework  of  the  building  (prefer- 


INSPECTION  OF  SUSPENDED  SCAFFOLDS  249 

ably  not  to  the  thrust -out  itself)  before  the  man 
is  permitted  to  go  out  upon  the  thrust -out.  The  rope 
should  be  no  longer  than  is  necessary  in  order  to  per- 
mit the  work  to  be  done  without  inconvenience, 
because  if  it  were  needlessly  long  the  fall  of  the  man 
would  subject  it  to  a  snapping  stress  of  unnecessary 
severity,  and  it  would  be  more  likely  to  break  than  it 
would  be  if  it  were  shorter. 

Lifelines  are  in  common  use  in  Germany  and 
England  for  work  similar  to  that  described  above, 
but  they  are  seldom  seen  in  the  United  States,  where 
it  is  often  hard  to  induce  the  workmen  to  wear  them 
even  when  they  are  provided,  unless  some  person  in 
authority  stands  by  and  insists  upon  it. 

No  man  should  be  permitted  to  go  out  upon  a 
thrust -out,  except  for  some  definite  object  the  attain- 
ment of  which  appears  to  be  worth  the  chances  that 
are  involved;  and  even  in  this  case  no  one  should  be 
permitted  to  do  so  except  the  man  or  men  designated 
for  the  purpose  by  the  foreman  in  charge  of  the  work. 

140.  Inspection  of  Suspended  Scaffolds.  One  of 
the  conditions  most  essential  to  safety  in  the  use  of  a 
suspended  scaffold  is  the  careful  inspection  of  its 
parts,  both  before  the  scaffold  is  erected  and  while 
it  is  in  service.  The  builder  usually  leases  the  scaffold 
that  he  is  to  use,  instead  of  owning  it  himself.  This 
is  believed  to  be  the  best  practice,  because  scaffold 
machines  are  mechanical  devices  of  a  very  special 
kind,  and  they  can  best  be  inspected  and  kept  in 
proper  condition  by  a  concern  that  makes  a  business 
of  doing  this  one  particular  thing.  The  company 
owning  the  scaffold  machine  furnishes  all  of  the  parts 
that  are  essential  to  the  erection  of  the  scaffold,  with 


250  SUSPENDED  SCAFFOLDS— EITHER  TYPE 

the  exception  of  the  planking  and  other  wooden  por- 
tions, and  the  side  shields  and  top  shields.  It  would 
be  much  better,  in  most  cases,  for  the  same  concern 
to  furnish  everything  complete, — wooden  parts  and 
all, — installing  the  scaffold  ready  for  use  in  all  respects, 
with  its  hand-rails,  foot-boards,  and  wire  netting 
(or  other  equivalent)  in  place. 

A  scaffold  that  has  been  used  should  never  be  put 
in  service  again  until  it  has  been  carefully  inspected 
in  every  part.  The  cables  should  be  unwound  from 
the  drums  and  examined  at  every  point,  to  see  if  any 
of  their  strands  have  become  broken,  or  if  they  have 
become  unduly  worn  or  damaged  in  any  other  way. 
The  fastenings  at  the  ends  of  the  cables  should  be 
particularly  examined,  to  see  that  they  are  in  good 
condition.  Every  nut  and  bolt  should  be  inspected 
also,  to  see  that  it  is  tight  and  sound.  In  a  word,  every 
portion  of  every  machine  should  be  gone  over  carefully 
and  conscientiously,  and  have  its  condition  thoroughly 
investigated  in  every  detail,  before  the  scaffold  is 
used  on  another  job.  It  is  impossible  to  throw  too 
great  an  emphasis  upon  the  importance  of  this  inspec- 
tion service,  and  builders  who  hire  scaffolds  should 
assure  themselves  in  every  case  not  only  that  the 
inspection  has  been  made,  but  also  that  it  has  been 
made  by  a  man  skilled  in  work  of  this  kind.  A  con- 
siderable proportion  of  the  accidents  that  have  occurred 
upon  the  suspended  scaffolds  that  are  used  in  construc- 
tion work  have  doubtless  been  due  to  neglect  in  this 
respect,  or  to  neglect  in  replacing  or  repairing  parts 
that  the  inspection  may  have  shown  to  be  faulty. 

The  scaffold  should  also  be  inspected  at  frequent 
intervals  while  it  is  in  service,  to  see  that  it  is  in  good 


INSPECTION  OF  SUSPENDED  SCAFFOLDS  251 

condition  at  all  points,  so  far  as  can  be  determined 
in  this  way.  (See  also  paragraph  155.)  In  making 
these  inspections,  particular  attention  should  be  paid 
to  the  positions  and  fastenings  of  the  thrust -outs, 
to  the  general  condition  of  the  machines,  to  the  visible 
parts  of  the  suspension  cables  (and  particularly  to 
their  ends,  where  these  can  be  seen),  to  the  planking 
of  the  platforms,  and  to  the  protective  hand-rails, 
foot -boards,  and  wire  netting.  The  inspection  of  the 
scaffold  while  it  is  in  service  should  likewise  include 
an  examination  of  those  parts  of  the  building  that 
are  higher  than  the  scaffold,  and  near  to  the  plane  of 
the  wall  that  is  going  up.  Heavy  objects  should  not 
be  stored  in  such  places,  nor  should  piles  of  brick  or 
other  materials  be  allowed  to  stand  where  they  may 
possibly  be  overthrown  in  such  a  way  as  to  fall  down 
upon  the  scaffold. 


XI.     SCAFFOLDS  OF  OTHER  KINDS. 

141.  General    Remarks.     It    is    unnecessary    to 
discuss  every  form  of  scaffold  with  the  same  degree  of 
detail  that  we  have  given  to  the  forms  that  have  been 
described  up  to  this  point,  because  the  same  general 
principles  apply  in  all  cases,  and  minute  description 
and  discussion  would  therefore  involve  much  useless 
repetition.     Moreover  it  would  be  impossible  to  take 
all  forms  of  scaffolds  into  account,  not  only  because 
they   are   used   for   an   exceedingly   great   variety   of 
special  purposes,  but  also  because  the  different  forms 
often  shade  into  one  another  by  modifications  that 
are   slight    and   even   non-essential.      In   the   present 
section,  however,  we  shall  take  up  a  few  forms  that 
it   appears  to   be   desirable   to  mention  explicitly, — 
calling  attention  to  certain  points  in  connection  with 
them  that  have  a  special  relation  to  the  safety  problem. 

142.  "Outrigger"  Scaffolds.     In  scaffolds  of  this 
kind  the  characteristic  and  essential  feature  is  the  sup- 
port of  the  platform  by  outwardly-projecting  beams 
(called    "thrust-outs",    "outriggers",     "jibs",    "canti- 
levers", "bearers",  and  various  other  names),  that  are 
supported  in  some  safe  way, — preferably  by  framework 
and  bracing,  inside  of  the  building.     The  protective  plat- 
form illustrated  in  Figs.  57,  58,  and  59  is  a  structure  of 
this  kind,  though  it  would  not  ordinarily  be  called  a 
scaffold,  because  it  is  not  intended  for  the  support  of 
men  or  materials.     Further  examples  are  shown  on  the 


OUTRIGGER  SCAFFOLDS  253 

left  of  Fig.  4,  on  the  right  of  Fig.  7,  and  in  Fig.  68. 
In  the  "outrigger"  or  "thrust -out"  scaffold  the  plat- 
form is  either  laid  directly  upon  the  thrust-outs,  or 
supported  from  them  immediately  and  without  the  in- 
tervention of  any  considerable  space  or  sustaining 
mechanism.  The  suspended  scaffolds  that  are  used  in 
construction  work  on  high  steel-framed  buildings,  and 
which  are  described  in  this  work  from  page  1 68  to  page 
210,  are  not  usually  classed  as  outrigger  scaffolds, 
because  although  they  are  supported  by  beams  that  are 
thrust  out  from  the  building,  they  are  of  such  a  special 
design  that  they  constitute  a  class  by  themselves. 

The  sustaining  beams  of  an  outrigger  scaffold 
should  never  be  merely  built  into  the  wall  and  left 
without  other  support.  They  should  always  project 
entirely  through  openings  in  the  wall,  or  through  win- 
dows, and  be  solidly  and  properly  supported  and  braced 
on  the  inside  of  the  building.  External  struts  and 
braces  should  be  used  wherever  they  may  be  needed  to 
provide  additional  strength  or  stiffness,  but  it  is  unwise 
to  place  any  great  reliance  upon  external  support  of 
this  kind,  unless  the  construction  is  exceptionally  well- 
designed  and  strong.  Some  engineers  approve  of  ex- 
ternal bracing  for  the  main  support,  if  it  is  secured  to 
iron  dogs  or  spikes  that  are  driven  into  stone  wTalls  and 
solidly  wedged ;  but  a  construction  of  this  kind  involves 
so  many  uncertainties  that  we  strongly  advocate  a 
more  positive  method  of  support. 

It  is  exceedingly  important,  in  all  cases,  to  use 
nothing  but  the  best  material  for  the  thrust -outs.  They 
should  be  strong  enough,  when  considered  as  beams 
supported  at  one  end,  to  sustain,  with  a  factor  of  safety 
of  at  least  ten,  the  heaviest  load  to  which  they  will  be 


254 


SCAFFOLDS  OF  OTHER  KINDS 


subjected;  and  the  same  consideration,  in  this  respect, 
should  also  be  paid  to  the  various  supports  and  fasten- 
ings upon  which  the  security  of  the  scaffold  depends. 

The  thrust -outs  should  be  rigidly  held,  so  that  no 
displacement  of  them  will  be  possible,  in  any  direction. 
Builders  often  fail  to  make  proper  provision  for  guard- 
ing them  against  sidewise  displacement,  even  when 
they  are  well  supported  so  far  as  direct  vertical  failure  is 
concerned.  Outriggers  having  a  rectangular  cross-sec- 
tion should  rest  on  their  edges,  because  they  have  the 
greatest  strength  in  that  position ;  and  they  should  be  se- 
cured so  that  they  cannot  turn  over  on  their  sides  while 
in  service,  not  only  because  they  would  then  be  weaker 
when  considered  as  beams,  but  also  because  the  shock  to 
which  the  scaffold  would  be  subjected  by  a  sudden  over- 
turning of  this  kind  would  throw  a  severe  stress  upon 
the  whole  structure,  and  perhaps  cause  it  to  give  way. 


FIG.  96.     INTERIOR  SUPPORTS  OF  AN  OUTRIGGER  SCAFFOLD. 

(From  the  new  German  Museum  building,  Munich.) 


OUTRIGGER  SCAFFOLDS  255 

Fig.  96  shows  the  interior  supports  of  a  thrust -out 
scaffold  that  was  used  in  the  construction  of  the  new 
German  Museum  building  at  Munich,  and  illustrates 
the  commendable  thoroughness  with  which  the  sup- 
porting work  was  designed  and  installed.  The  plat- 
form of  the  scaffold,  which  cannot  be  seen  in  the 
engraving  because  it  was  outside  of  the  building,  was 
substantially  on  a  level  with  the  tops  of  the  window 
openings. 

Fig.  97  shows  a  church  spire,  surrounded  with  an 
extensive  scaffold  resting  upon  outriggers  set  at  or 
near  the  base  of  the  tapered  part  of  the  spire.  Work 
of  this  kind  should  never  be  attempted  by  anybody 
but  an  expert  in  scaffold  construction,  and  the  out- 
riggers that  support  the  structure  should  be  selected 
and  placed  with  special  care.  Steel  outriggers  are  pre- 
ferable to  wooden  ones,  in  such  cases,  on  account  of 
their  superior  strength ;  and  they  should  run  completely 
through  the  spire,  from  side  to  side.  It  is  often  difficult 
and  always  expensive  to  obtain  sound  wooden  beams 
of  proper  size  and  strength  for  purposes  of  this  kind. 

Hand-rails  and  toe-boards,  or  other  protective  de- 
vices equivalent  to  them,  are  as  important  on  thrust  - 
out  scaffolds  that  are  to  be  used  by  workmen  as  they 
are  on  scaffolds  of  other  forms  that  are  situated  at 
similar  heights.  There  is  seldom  any  special  difficulty 
in  providing  safeguards  of  this  kind,  and  there  is 
correspondingly  little  excuse  for  omitting  them.  Fig. 
98  shows  an  outrigger  scaffold  that  was  well  con- 
structed and  supported,  and  which  was  provided  also 
with  two  guard-rails,  a  foot -board,  and  a  side  screen 
of  wire  netting.  The  platforms  of  outrigger  scaffolds 
are  frequently  built  with  tight  board  fences  along  their 


256 


SCAFFOLDS  OF  OTHER  KINDS 


outer  edges,  so  that  neither  men  nor  materials  can  fall 
from  them.  (See,  for  example,  Fig.  119  on  page 
300,  which  shows  a  protective  scaffold  supported  by 
outriggers.) 


FIG.  97.     FRAMEWORK  SCAFFOLD  SUPPORTED  BY  OUTRIGGERS. 


OUTRIGGER  SCAFFOLDS 


257 


FIG.  98.     A  WELL-CONSTRUCTED  OUTRIGGER  SCAFFOLD. 

As  pointed  out  in  paragraphs  75  and  149,  out- 
rigger scaffolds  may  often  be  used  to  advantage  as  pro- 
tective roofs  over  passageways  or  workplaces,  and  as 
"catch -plat forms"  to  prevent  the  fall  of  materials  upon 
persons  at  lower  levels,  or  to  prevent  fatal  conse- 
quences in  case  workmen  should  fall  from  another 
platform  or  workplace  at  a  somewhat  greater  height. 
They  are  also  useful  for  roofers,  tinners,  painters,  or 
carpenters,  when  doing  light  work  on  cornices  or  gut- 
ters or  in  other  elevated  places.  Nevertheless,  we  do 
not  advise  the  use  of  outrigger  scaffolds  for  the  sup- 
port of  workmen  when  some  other  form  can  be  used 
with  equal  advantage,  b'ecause  although  they  can  be 
made  quite  safe,  it  often  happens  that  the  men  who 


258  SCAFFOLDS  OF  OTHER  KINDS 

are  charged  with  erecting  them  do  not  thoroughly 
understand  the  mechanical  principles  that  are  involved, 
or  do  not  take  the  time  or  trouble  to  do  the  work  with 
proper  thoroughness. 

When  outrigger  scaffolds  are  to  be  employed  they 
should  be  carefully  inspected,  before  they  are  used,  by 
a  competent,  painstaking  man,  who  understands  just 
what  is  required  and  who  has  authority  to  have  every 
weak  or  doubtful  element  in  the  construction  replaced 
or  strengthened.  Scaffolds  of  this  kind  should  never 
be  used  for  supporting  heavy  loads,  unless  they  have 
been  designed  and  built  with  special  reference  to  such 
loads,  under  the  direction  of  a  person  who  is  competent 
to  calculate  the  stresses  that  will  be  thrown  upon  them 
in  every  part,  and  who  has  investigated  these  stresses, 
and  provided  for  them,  with  all  the  care  that  would  be 
exercised  in  connection  with  a  permanent  structure. 

In  placing  the  thrust-outs  of  an  outrigger  scaffold, 
and  in  laying  upon  them  the  planking  or  other  super- 
structure that  they  may  have  to  support,  the  greatest 
care  should  always  be  taken  to  protect  the  men  from 
falling,  and  to  prevent  accidents  from  the  fall  of 
materials  or  of  parts  of  the  scaffold.  The  same  counsel 
applies,  also,  to  the  dismantling  of  such  scaffolds. 

143.  Carpenters'  Scaffolds.  Carpenters  make  use 
of  scaffolds  of  various  kinds,  the  most  familiar  and  dis- 
tinctive of  which  consists  of  a  platform  of  boards,  sup- 
ported by  brackets  or  "jacks"  that  are  secured  to  the 
side  of  the  building.  Fig.  99  shows  a  well-designed 
bracket  for  a  scaffold  of  this  kind  that  is  to  be  used  in 
ordinary  work,  where  no  great  weight  has  to  be  sup- 
ported. In  using  a  jack  of  this  kind,  carpenters  some- 
times pass  the  supporting  bolt  merely  through  the 


CARPENTERS'  SCAFFOLDS 


259 


FIG.  99.     A  CARPENTERS'  BRACKET  OR  "JACK." 

(Each  piece  is  13/£  in.,  full,  in  thickness.    Selected  spruce  is  recommended.) 

outer  sheathing  of  the  building,  placing  entire  reliance 
upon  the  holding  power  of  the  nails  by  which  the 
sheathing  is  attached  to  the  studding.  This  practice 
is  unsafe.  To  support  the  bracket  properly,  a  block 
should  be  laid  across  the  space  between  two  consecu- 
tive vertical  studs,  so  as  to  rest  against  them  on  the 
inside;  and  the  bolt  should  then  be  passed  not  only 
through  the  sheathing  but  also  through  the  block,  the 
nut  of  the  bolt  being  screwed  down  solidly  against  the 
block  with  a  substantial  washer  between.  The  tension 
on  the  supporting  bolt  is  thus  transferred  directly  to 
the  studs,  and  a  correspondingly  greater  degree  of 
safety  is  assured. 

The  bracket  should  have  its  supporting  bolt  near 
the  top,  and  the  threads  should  be  in  good  condition  both 
on  the  bolt  and  on  the  nut.  The  bolt  should  be  of 
generous  size,  and  long  enough  to  go  through  the 


260  SCAFFOLDS  OF  OTHER  KINDS 

sheathing  and  be  secured  in  the  manner  recommended 
above,  and  to  project  for  at  least  a  couple  of  inches 
beyond  the  nut  when  the  bracket  has  been  secured  in 
position.  The  nut  should  also  fit  tightly  on  the  thread, 
so  that  it  cannot  work  loose  while  the  scaffold  is  in 
service. 

The  material  that  is  used  in  the  scaffold  should  be 
first-class  throughout,  in  all  respects.  This  point  does 
not  always  receive  the  attention  that  it  merits,  and  the 
men  are  often  tempted  to  use  inferior  material  for  the 
scaffold,  and  to  put  the  better  stock  into  the  building. 
It  is  much  better  and  safer  to  reverse  the  procedure, 
and  put  the  poorer  material  into  the  building.  The 
brackets  and  platform-boards  should  both  be  excep- 
tionally sound  and  strong,  and  when  they  have  become 
deteriorated  from  protracted  use  or  from  exposure  to 
the  weather,  they  should  be  discarded  and  replaced  by 
new  ones.  Brackets  that  have  become  broken  or  other- 
wise damaged  or  weakened  are  often  seen  in  use,  but  it 
is  poor  economy  to  continue  them  in  service  when  they 
are  in  bad  condition,  and  many  serious  accidents  result 
from  following  this  course. 

It  is  very  common  indeed  for  carpenters  to  lay  the 
platform  boards  of  scaffolds  so  that  they  project  over 
the  brackets  and  form  what  are  known  as  "traps". 
This  name  refers  to  the  analogy  between  such  plat- 
forms and  certain  forms  of  animal  traps,  in  which  the 
victim  is  led  to  step  upon  a  surface  that  is  apparently 
safe,  but  which  immediately  tips  under  his  weight  and 
allows  him  to  fall  into  an  inclosure.  Every  possibility 
of  this  kind  should  be  carefully  avoided,  by  laying  the 
platform  so  that  no  board  projects  over  a  bracket,  at 
either  end,  by  more  than  six  or  eight  inches,  without 


CARPENTERS'  SCAFFOLDS  261 

support.  Fig.  100  illustrates  what  may  be  called  a 
''blind  trap".  A  man  walking  along  a  platform  laid  in 
this  way  could  easily  be  deceived  as  to  the  positions  of 
the  supporting  brackets,  and  might  therefore  be  led 
to  step  with  firmness  and  confidence  upon  exceedingly 
dangerous  places. 

In  addition  to  avoiding  traps,  it  is  important  to 
have  the  platforms  thick  enough  to  prevent  any  con- 
siderable amount  of  springiness,  or  yielding,  near  the 
middle  points  of  the  boards.  The  yielding  can  be  pre- 
vented in  large  measure  by  setting  the  supporting 


FIG.  100.     ILLUSTRATING  A  "BLIND  TRAP"  ON  A  CARPENTERS' 

SCAFFOLD. 

(The  boards  overlap,  as  will  be  seen,  midway  between  two  brackets,  instead  of  squarely 
upon  one  of  the  brackets.  A  man  stepping  on  the  platform,  where  indicated  by  the  arrow, 
would  iall  down  through  it.) 

brackets  near  together.  There  should  be  three  brackets 
under  each  board,  and  two  layers  of  boards  should  be 
used,  if  necessary,  in  order  to  obtain  the  necessary 
rigidity  in  the  platform.  The  boards  should  be  laid 
snugly  together  so  that  there  will  be  no  room  for  tools 
or  materials  to  fall  down  between  them. 

Guard-rails  are  seldom  used  on  carpenters'  scaf- 
folds, although  there  is  no  special  difficulty  in  design- 
ing a  bracket  that  will  afford  good  support  to  a  guard- 
rail. When  the  bracket  is  of  the  ordinary  construction 
an  outwardly-projecting  piece  may  be  tacked  along  its 
horizontal  leg,  and  then,  by  means  of  a  diagonal  brace 
set  at  an  angle  of  about  4  5  degrees,  a  good  substantial 


262  SCAFFOLDS  OF  OTHER  KINDS 

support  can  be  had  for  the  railing  and  for  a  foot-board 
also. 

For  shingling  and  roofing,  angle  brackets  (also 
known  as  "jacks"  or  "cripples")  are  often  used,  having 
sharp  points  that  are  thrust  into  the  roof  to  prevent 
sliding.  It  is  much  safer,  however,  to  support  the 
brackets  by  means  of  ropes  passing  over  the  ridgepole 
of  the  building.  When  dependence  is  placed  upon 
pointed  projections  to  hold  the  brackets  in  position,  see 
that  the  points  are  secure  and  in  good  condition,  and 
that  they  penetrate  to  their  full  length  in  the  wood- 
work of  the  building.  If  ropes  are  used,  see  that  they 
are  strongly  fastened,  not  only  to  the  scaffold  brackets 
but  also  to  substantial  projections  such  as  chimneys  or 
cupolas,  or  to  solidly -fixed  objects  on  the  further  side 
of  the  building.  They  may  also  be  secured  by  means 
of  bolts  having  a  diameter  of  not  less  than  5/8  of  an 
inch,  provided  at  one  end  with  a  long  wood -screw  to 
screw  into  the  timbers,  and  at  the  other  end  with  a 
strong,  well-shaped  eye  for  receiving  the  rope.  If  eye- 
bolts  are  used  in  this  way,  they  should  be  solidly 
screwed  into  sound,  heavy  timbers,  and  not  merely 
screwed  through  a  thickness  of  board. 

When  ropes  are  used  in  any  of  these  ways,  it  is 
important  to  be  sure  that  they  are  in  good  condition  in 
every  respect,  and  that  they  do  not  catch  upon  pro- 
jections from  which  they  may  become  loosened  while 
in  service,  so  as  to  let  the  scaffold  drop  by  even  a  short 
distance,  with  a  resulting  chance  of  precipitating  the 
workmen  to  the  ground. 

In  laying  shingles,  carpenters  often  work  without 
the  aid  of  brackets,  relying  for  support  upon  horizon- 
tally-placed pieces  of  scantling  arranged  as  follows. 


CARPENTERS'  SCAFFOLDS  263 

A  long  piece  of  material,  about  2  inches  by  4  inches  in 
section,  has  several  shingles  securely  nailed  to  it  at  dif- 
ferent parts  of  it's  length,  in  such  a  way  that  the  butt 
of  each  shingle  comes  flush  with  the  edge  of  the  scant- 
ling. The  whole  thing  is  then  turned  over  so  that  the 
shingles  come  next  to  the  roof,  and  each  shingle  is 
nailed  solidly  to  the  building  so  that  the  upper  edge  of 
the  scantling  coincides  with  the  lower  edge  of  the 
next  course  of  shingles.  The  men  rely  upon  these 
pieces  of  scantling  for  support,  and  the  work  proceeds 
until  shingles  have  been  laid  to  such  a  height  that  con- 
venience requires  another  strip  to  be  placed  in  position 
in  like  manner.  In  removing  the  strips  of  scantling 
after  the  work  is  completed,  some  carpenters  merely 
cut  off  the  shingles  to  which  they  are  nailed,  leaving 
the  thin  upper  ends  of  these  shingles  in  position.  This 
cannot  be  regarded  as  first  -class  practice,  however,  be- 
cause it  leaves  slight  bulges  on  the  roof.  To  overcome 
this  objection,  the  shingles  that  served  to  support  the 
scantling  are  often  removed  by  striking  them  sharply 
to  the  right  and  left,  so  as  to  break  the  hold  of  the 
nails  by  which  they  are  secured  to  the  roof, — after 
which  they  can  usually  be  removed  without  difficulty. 
The  rough  work  of  extracting  the  shingles  is  likely  to 
loosen  other  shingles  in  the  vicinity,  however,  and  for 
this  reason  many  carpenters  now  nail  the  scantlings  to 
the  roof  by  means  of  strips  of  sheet  zinc.  When  the 
shingling  is  finished  the  zinc  strips  are  cut  off  flush 
with  the  edges  of  the  shingles  that  overlap  them,  and 
left  in  position.  They  ,do  no  harm,  because  they  are 
too  thin  to  cause  the  overlapping  shingles  to  stand  up 
to  any  sensible  extent  from  those  below.  The  cost  of 
the  zinc  is  not  a  serious  element,  and  at  the  usual  price 


264  SCAFFOLDS  OF  OTHER  KINDS 

of  the  metal  it  need  not  amount  to  more  than  about 
one  dollar  to  every  hundred  thousand  shingles. 

Crawling -boards  (known  also  as  "step -boards", 
* 'chicken-ladders",  or  "duck-ladders")  should  be  used 
wherever  they  will  tend  to  promote  safety.  A  crawling- 
board  consists  of  a  board,  preferably  9  inches  or  more 
in  width  and  at  least  1  1/4  inches  thick,  to  which 
conveniently -spaced  cross-strips  are  nailed,  each  about 
1  1/2  inches  wide  and  1  inch  thick.  It  is  laid  upon  the 
roof  so  that  its  length  extends  from  the  ridge-pole 
down  toward  the  eaves,  and  is  used  to  assist  the  work- 
men in  passing  from  one  part  of  the  roof  to  another. 
Crawling-boards  should  be  securely  fastened,  so  that 
they  cannot  become  loose  and  slide  down  the  roof.  It 
is  best  to  make  them  double,  as  shown  in  Fig.  105, 
and  to  lay  them  across  the  roof  with  the  hinge  at  the 
peak  or  ridge-pole  as  there  indicated.  They  may  like- 
wise be  secured  by  hooks  attached  to  them  at  their 
upper  ends,  and  arranged  so  as  to  reach  over  the  peak 
of  the  roof  and  seize  the  building  on  the  other  slope. 
They  are  also  made  with  thick,  solidly-fastened  cleats 
on  the  under  side,  at  the  upper  end,  to  hook  over  the 
peak,  or  with  one  or  more  bolts  projecting  through 
the  upper  ends,  to  catch  over  the  peak  in  like  manner. 
If  a  cleat  or  bolt  is  used,  we  advise  nailing  the  crawling- 
board  down  at  the  upper  end,  in  addition,  to  remove  all 
possibility  of  the  board  or  the  bolt  becoming  displaced 
in  an  upward  direction,  sufficiently  to  loosen  the  hold. 

When  a  considerable  amount  of  work  is  to  be  done 
on  a  steep  roof  having  an  average  height  of  more  than 
20  feet  (as  measured  from  the  ground  to  the  eaves),  it 
is  exceedingly  important  to  provide  a  catch -platform  or 
some  equivalent  device,  to  save  the  men  from  injury 


PAINTERS'  SWINGING  SCAFFOLDS  265 

in  case  the  brackets  on  the  roof  give  way  or  any  other 
accident  occurs.  If  the  roof  has  a  parapet  at  the  eaves, 
the  protection  afforded  in  this  way  may  be  quite  suf- 
ficient ;  or  if  there  is  a  pole  scaffold  or  other  scaffold 
already  standing  by  the  side  of  the  building,  and  hav- 
ing a  wide,  substantial,  well-supported,  and  well- 
guarded  platform  at  the  eaves  or  immediately  below 
them,  this  should  afford  satisfactory  protection.  If 
neither  of  these  conditions  is  fulfilled,  a  special  pro- 
tective platform  of  some  kind  should  be  provided  at 
the  eaves  or  slightly  below  them.  A  thrust-out  scaf- 
fold, securely  supported,  with  a  platform  about  45 
inches  wide  located  not  more  than  30  inches  below  the 
eaves,  is  satisfactory  for  this  purpose,  if  properly  pro- 
vided with  guard-rails  and  foot-boards.  (See  also 
paragraphs  142  and  149.) 

When  the  work  to  be  done  on  the  roof  is  not  ex- 
tensive enough  to  justify  the  labor  and  expense  in- 
volved in  erecting  a  special  protective  platform  at  the 
eaves,  or  when  for  any  other  special  reason  it  is  deemed 
inexpedient  to  construct  such  a  platform,  the  workmen 
should  be  provided  with  strong  life  lines,  securely 
attached  to  fixed  parts  of  the  building.  (See  para- 
graph 139.) 

The  forms  of  scaffold  that  are  used  by  carpenters 
for  interior  work  do  not  differ  sufficiently  from  those 
employed  by  plasterers  and  decorators,  and  described 
in  paragraph  146,  to  call  for  separate  description 
and  discussion. 

144.  Painters'  Swinging  Scaffolds.  The  painters' 
swinging  scaffold  in  its  typical  form  consists  of  a  short, 
light  platform,  supported  at  the  ends  by  ropes  that  are 
attached  to  the  building  at  the  eaves  or  at  some  other 


266 


SCAFFOLDS  OF  OTHER  KINDS 


elevated  point.  The  platform  often  consists  of  boards 
laid  upon  a  horizontal  ladder  of  special  construction, — • 
its  side-bars  being  parallel  and  somewhat  further 
apart  than  usual.  Each  end  of  the  ladder  is  supported 
by  an  iron  stirrup  or  hanger  (similar  to  the  one  shown 
in  Fig.  101) .  which  also  serves  for  attaching  the  suspen- 
sion rope.  The  hangers  should  be  so  formed  that 
guard-rails  can  easily  be  secured  to  them,  to  protect  the 
men  from  falling  over  the  edge  of  the  platform.  The 
ladder  is  often  strengthened  by  means  of  small  wire 
ropes,  about  5/16  of  an  inch  in  diameter,  which  extend 
along  the  under  surfaces  of  the  side-bars,  from  end  to  end. 


^   FOR 
SUSPENSION 
HOOK 


FIG.  101.     AN  APPROVED  FORM  OF  PAINTERS'  HANGER. 

(The  wheels  or  rollers  are  not  shown.    See  Figs.  102,  103,  and  104.) 

The  suspension  ropes  are  arranged  to  run  through 
blocks  so  that  the  men  can  easily  raise  or  lower  the  stag- 
ing, the  hook  of  the  lower  block  engaging  in  an  eye  or 
loop  in  the  upper  part  of  the  hanger.  The  suspension 
rope  is  made  fast  to  the  point  of  the  hook  by  means  of 
a  special  hitch,  which  is  shown  in  the  accompanying 


PAINTERS'  SWINGING  SCAFFOLDS 


267 


268  SCAFFOLDS  OF  OTHER  KINDS 

illustrations  (Figs.  102,  103,  and  104).  This  hitch  is 
exceedingly  simple,  and  is  secure  when  it  is  correctly 
made;  but  no  person  should  undertake  to  use  it  in 
actual  work  until  he  has  been  carefully  instructed  by  a 
man  of  experience. 

There  is  a  considerable  amount  of  free  rope  to  every 
1  'fall",  especially  when  the  staging  is  at  the  higher 
levels.  This  is  usually  allowed  to  lie  upon  the  ground, 
but  it  is  a  much  better  practice  to  coil  it  up  at  the  plat- 
form of  the  staging,  because  there  is  then  no  danger  of 
interference  with  the  scaffold  by  teams  or  by  curious  or 
meddlesome  persons.  Moreover,  when  the  excess  rope 
is  left  on  the  ground  there  is  danger  that  it  may  be- 
come wet  with  acid  that  may  be  used  for  cleaning  the 
walls  of  the  building.  Accidents  from  this  source  often 
happen,  the  acid  soaking  into  the  rope  and  ruining  its 
inner  fibers,  so  that  the  rope  has  no  strength  even 
though  when  superficially  examined  it  looks  to  be  in 
good  condition.  If  the  rope  is  secured  to  the  plat- 
form, it  is  completely  under  the  control  of  the  work- 
men who  are  using  the  staging,  and  it  is  also  out  of 
the  way  of  possible  harm. 

In  view  of  the  danger  from  acid  rot,  or  from  grad- 
ual weakening  from  simple  exposure  to  the  weather,  the 
ropes  that  are  used  on  painters'  scaffolds  should  be 
thoroughly  tested  from  time  to  time,  to  a  stress  that 
is  materially  in  excess  of  any  lead  that  is  likely  to  be 
thrown  upon  them  in  use.  The  full  effects  of  acid  do 
not  develop  for  several  weeks,  as  a  rule,  and  ropes  that 
may  have  been  exposed  to  it  should  therefore  be 
allowed  to  remain  out  of  use  for  at  least  eight  or  ten 
weeks,  before  testing,  in  order  to  avoid  the  drawing  of 
wrong  conclusions  from  the  test. 


PAINTERS'  SWINGING  SCAFFOLDS  269 

In  addition  to  the  tension  test  that  is  here  advised 
for  the  ropes,  the  entire  scaffold  should  be  tested  every 
time  it  is  erected,  and  before  any  person  is  allowed  to 
use  it.  For  this  purpose  the  platform  should  be  raised 
a  foot  or  so  from  the  ground,  and  loaded  with  at  least 
four  times  the  maximum  wreight  that  it  will  be  called 
upon  to  sustain  in  the  subsequent  work.  (See  para- 
graph 147.)  If  it  shows  no  sign  of  weakness  under  this 
test,  it  may  be  considered  to  be  safe  to  use. 

When  leaving  a  swinging  scaffold  of  this  kind,  the 
men  should  always  lower  the  platform  to  the  ground, 
or  lash  it  securely  to  the  building,  so  that  it  cannot  be 
blown  about  by  the  wind ;  and  they  should  never  leave 
buckets  or  other  objects  on  it,  that  might  become  dis- 
placed and  fall  upon  persons  below. 

The  platform  of  the  staging  should  be  provided 
with  wooden  rollers  or  wheels  some  6  inches  or  so  in 
diameter,  which  will  bear  against  the  side  of  the  build- 
ing that  is  to  be  painted.  (See  Figs.  102,  103,  and 
104.)  These  hold  the  staging  at  a  proper  distance  from 
the  wall,  and  also  make  it  easier  to  manipulate  the  plat- 
form when  it  is  necessary  to  shift  it  to  a  new  level. 

The  hooks  that  are  used  to  support  the  scaffold, 
and  which  constitute  the  usual  means  of  attaching  it 
to  the  building,  should  be  of  generous  size,  and  should 
be  well  made,  and  constructed  of  first-class  material. 
Every  time  they  are  used  they  should  be  carefully  ex- 
amined for  flaws  or  other  similar  imperfections,  and 
further  tested  by  ringing  them  on  a  stone  sidewalk  or 
in  some  other  equivalent  way.  See  that  they  are  well 
anchored,  and  that  the  woodwork  to  which  they  are  se- 
cured is  sound  and  safe.  Do  not  set  them  into  decayed 
wood,  nor  into  wood  that  is  in  any  way  open  to  criti- 


270  SCAFFOLDS  OF  OTHER  KINDS 

cism  with  respect  to  its  soundness  or  strength.  If 
necessary,  lay  down  a  new  plank  and  secure  the  hooks 
to  this,  nailing  the  plank  in  position  whenever  it 
appears  to  be  desirable  to  do  so. 

On  flat -topped  buildings  painters  often  use  a  form 
of  hook  or  "cornice  iron"  consisting  of  a  straight  bar 
of  steel  bent  at  a  sharp  right  angle  near  its  middle 
point,  and  having  an  eye  forged  at  the  end  of  each  arm. 
When  an  iron  of  this  form  is  used  it  should  be  set  so 
that  its  angle  fits  snugly  over  the  edge  of  the  cornice, 
with  one  arm  extending  downward  and  the  other  lying 
horizontally  along  the  roof,  at  right  angles  to  the  edge. 
The  eye  at  the  end  of  the  overhanging,  vertical  arm 
sustains  one  of  the  suspension  ropes  of  the  scaffold, 
while  the  eye  at  the  end  of  the  horizontal  arm  affords 
a  means  of  making  the  iron  fast  to  a  chimney  or  other 
solid  and  substantial  object  on  the  roof.  Cornice  irons 
of  this  type  afford  an  excellent  support  when  they  are 
applied  as  here  described, — provided  they  are  well  made, 
from  first-class  stock  of  proper  size;  and  provided,  fur- 
thermore, the  cornice  is  itself  strong  and  secure.  More 
commonly,  however,  the  hook  is  made  in  the  general 
shape  of  an  interrogation  mark,  so  that  it  may  pass  with 
a  smooth,  easy  curve  over  the  edge  of  the  eaves  or  other 
projections,  to  the  upper  side  of  which  it  is  secured. 

When  there  is  difficulty  in  attaching  the  hooks  to 
the  building,  the  scaffold  is  often  supported  by  means  of 
ropes  that  are  passed  over  the  peak  of  the  roof,  and 
brought  down  to  the  other  side  and  made  fast  to  some 
fixed  object.  This  method  of  attachment  is  excellent, 
provided  the  ropes  that  extend  over  the  roof  are  suf- 
ficient in  size,  and  are  known  to  be  in  good  condition,, 
and  are  securely  fastened. 


PAINTERS'  SWINGING  SCAFFOLDS 


271 


FIG.  105.     DOUBLE  CRAWLING-BOARD,   OR   "CHICKEN-LADDER." 

(The  two  parts  are  alike,  and  are  joined  at  the  top  by  a  hinge.  The  hinge  bolt  should 
be  about  one  inch  in  diameter,  and  it  may  be  removed  to  facilitate  transportation  or  to 
allow  either  ladder  to  be  used  singly.  Crawl  ing-boards  are  also  used  in  shingling,  and  in 
working  on  roofs  of  tile  or  slate.  The  side  strips  which  are  here  shown  may  then  be  omit- 
ted, and  the  hinge  may  also  be  omitted  if  the  boards  are  to  be  used  singly, — provided  they 
are  effectively  secured,  as  explained  in  paragraph  143.  The  whole  construction  may  also  be 
somewhat  lighter,  when  the  appliance  is  to  serve  merely  to  assist  the  workmen  in  passing 
from  one  part  of  the  roof  to  another.) 

Never  work  on  a  painters'  staging  with  another 
man  who  is  likely,  for  any  reason,  to  do  anything  that 
might  add  to  the  natural  hazards  that  cannot  be  sepa- 
rated from  work  of  this  kind. 

In  painting  under  the  peak  of  a  roof  it  is  often  con- 
venient to  secure  the  hooks  to  a  special  support  con- 
sisting of  two  planks  joined  at  their  ends  by  a  stout 
hinge,  and  laid  over  the  roof  so  that  the  hinge  comes 
exactly  at  the  peak,  with  the  planks  lying  in  contact 
with  both  sides  of  the  roof.  (See  Fig.  105.)  Stout 
cleats,  at  least  11/4  inches  high  and  two  inches  wide, 
should  be  securely  nailed  to  the  planks  at  intervals  of 
a  foot  or  so,  and  each  hook  should  be  set  into  one  of  the 
planks  in  such  a  position  that  it  will  be  well  supported 
by  a  cleat.  Raised  strips  should  also  be  nailed  to  the 
edges  of.  the  planks,  to  prevent  the  hooks  from  slipping 
off  in  case  of  any  accidental  shifting  that  may  occur  in 


272  SCAFFOLDS  OF  OTHER  KINDS 

the  course  of  the  work;  and  the  planks  themselves 
should  be  tacked  down  to  the  roof  for  the  same  reason. 

Two  or  more  swinging  scaffolds  of  the  general 
type  here  described  should  never  be  combined  into  one 
by  bridging  the  interval  between  them  with  planks. 

In  some  localities  the  number  of  men  that  may 

J 

work  upon  a  swinging  scaffold  of  this  type  is  limited  by 
law,  and  we  strongly  advise  that  the  number  be  restric- 
ted to  two,  even  though  the  local  ordinance  may  allow 
more  than  this. 

145.  Needle-beam  Scaffolds.  A  form  of  scaffold 
that  is  widely  used  in  riveting  up  the  steelwork  of 
buildings,  making  light  repairs,  laying  corrugated-iron 
roofs,  and  performing  various  other  kinds  of  work  in 
which  the  men  frequently  shift  about  from  one  place  to 
another,  consists  of  a  plank  platform  resting  upon  two 
parallel  horizontal  beams  (called  "needle-beams"), 
which  are  supported  at  the  ends  by  ropes.  These  scaf- 
folds are  not  supposed  to  carry  any  considerable  weight, 
but  are  merely  for  the  support  of  men  while  they  do 
light  work  that  does  not  require  the  use  of  more  than  trifl- 
ing quantities  of  material.  When  the  needle-beams  are 
not  more  than  ten  or  twelve  feet  in  length  between  sup- 
ports, it  is  customary  to  make  them  four  inches  wide 
and  six  inches  deep ;  but  when  the  conditions  are  severe 
or  unusual,  this  size  must  be  increased  in  accordance 
with  the  length  of  the  beams,  and  the  weight  that  is  to 
be  supported.  For  example,  in  one  case  that  recently 
came  to  our  attention  a  scaffold  of  this  kind  was  used 
for  dressing  the  under  surfaces  of  the  arches  of  a  con- 
crete bridge,  and  as  there  was  no  way  in  which  to  sup- 
port the  needle-beams  under  the  arches,  they  were 
made  long  enough  to  extend  under  the  entire  width  of 


NEEDLE-BEAM  SCAFFOLDS 


273 


the  bridge.  This  made  the  span  of  each  needle-beam 
about  fifty  feet,  and  for  a  beam  of  this  length  the  cross- 
section  mentioned  above  would  be  totally  inadequate. 
The  beams  used  in  the  case  here  cited  were  eight  inches 
square,  and  were  made  of  material  that  was  first-class 
in  all  respects.  Every  needle-beam  should  in  fact  be 
made  of  straight -grained  selected  stock,  and  should  be 
free  from  knots,  shakes,  and  weaknesses  of  every  other 
kind.  (For  an  illustration  of  a  needle -beam  that  did 
not  fulfill  these  conditions,  see  Fig.  126.)  Selected 
spruce  may  be  used,  or  first-class  long -leaf  yellow  pine. 
Spruce  is  much  the  lighter  of  the  two,  and  it  is  prefer- 
able for  that  reason ;  but  it  must  be  of  exceptionally 
good  quality. 


FIG.  106.     ILLUSTRATING  THE  "SCAFFOLD  HITCH." 


274  SCAFFOLDS  OF  OTHER  KINDS 

In  handling  needle-beams,  great  care  should  be 
taken  to  avoid  injuring  them.  They  should  never  be 
dropped,  but  should  be  lowered  with  care  so  that  they 
will  not  become  broken,  split,  or  seriously  indented.  It 
is  easy  to  imagine  the  result  of  dropping  a  heavy  50-foot 
needle-beam  from  a  considerable  height,  so  that  it  falls 
centrally  across  a  stone  or  a  pile  of  lumber.  It  would 
almost  certainly  become  damaged  so  that  it  could  not 
be  used  with  safety  for  a  like  purpose  in  another  place. 

The  rope  that  is  used  for  supporting  the  needle - 
beams  should  be  first -class  in  quality,  and  should  be 
made  of  pure  manila  fiber.  It  should  be  attached  to 
each  needle -beam  by  means  of  what  is  known  as  a 
"scaffold  hitch",  which  is  shown  in  Fig.  106,  the  loose 
end  being  finally  tied  to  the  main  supporting  rope  by 
a  bowline  knot.  The  scaffold  hitch  should  be  arranged 
upon  the  needle-beam  as  shown  in  the  illustration,  and 
if  it  is  applied  properly  it  will  prevent  the  needle-beam 
from  rolling  or  becoming  otherwise  displaced.  The 
size  of  the  rope  should  be  appropriate  to  the  weight 
that  is  to  be  supported,  including  that  of  the  work- 
men as  well  as  that  of  the  scaffold  itself.  In  practice 
it  usually  ranges  in  diameter  from  one  inch  to  an  inch 
and  a  quarter ;  and  it  should  never  be  attached  to  the 
needle-beam  at  a  point  less  than  one  foot  from  the  end 
of  the  beam. 

As  already  noted,  needle-beam  scaffolds  are  often 
used  for  only  a  brief  period  in  any  one  position,  and 
for  that  reason  they  are  commonly  put  up  with  very 
little  regard  for  safety.  This  is  a  great  mistake,  because 
a  man  may  be  badly  hurt  by  falling  from  a  scaffold 
that  is  soon  to  be  moved,  just  as  readily  as  he  can  by 
falling  from  one  that  is  to  stand  for  a  year ;  and  the  fore- 


NEEDLE-BEAM  SCAFFOLDS  275 

man  in  charge  of  the  work  should  see  to  it,  personally, 
that  every  one  of  these  scaffolds  is  made  safe  before  the 
men  are  allowed  to  use  it. 

Opinions  differ,  among  safety  experts  who  have 
given  attention  to  the  subject  of  scaffolding,  as  to  the 
wisdom  of  erecting  guard-rails  on  needle-beam  scaf- 
folds, and  some  maintain  that  the  guard-rail  may  even 
constitute  an  additional  hazard  under  certain  circum- 
stances. For  example,  when  it  is  necessary  for  a 
man  to  swing  a  maul,  an  accident  may  be  caused  by  the 
maul  fouling  the  guard-rail.  Furthermore,  it  is  some- 
times almost  impossible  to  erect  a  guard-rail,  owing  to 
the  place  in  which  the  scaffold  is  to  be  used ;  and  it  is  a 
fair  question  whether  or  not  it  is  wise  to  use  guard-rails 
in  some  places  and  not  in  others,  with  the  same  type 
of  scaffold  and  the  same  gang  of  men ,  because  if  they 
come  to  rely  upon  the  guard-rail  when  it  is  used,  this 
habit  may  cause  them  to  fall  at  some  time  when  it  is 
not  used.  The  best  conclusion  that  we  can  draw  with 
regard  to  this  matter  appears  to  be  that  the  foreman 
should  carefully  consider  each  case  on  its  own  merits, 
and  should  erect  the  guard-rails  or  omit  them,  according 
to  his  best  judgment,  with  due  reference  to  the  place 
w7here  the  scaffold  is  to  be  used  and  the  nature  of  the 
work  that  is  to  be  done  upon  it.  Although  we  main- 
tain that  a  rope  railing  is  never  as  good  as  a  railing  of 
wood  or  metal,  it  is  often  better  than  no  railing  at 
all,  and  it  can  sometimes  be  used  where  a  more  sub- 
stantial protection  is  out  of  the  question. 

As  a  rule,  the  plank  floorings  of  these  needle-beam 
scaffolds  are  much  more  serious  sources  of  trouble  than 
the  guard-rails.  The  men  are  often  permitted  to  work 
with  altogether  too  few  planks,  or  with  planks  that  are 


276  SCAFFOLDS  OF  OTHER  KINDS 

poor  in  quality,  or  of  insufficient  length.  The  foreman 
should  always  see  that  the  flooring  is  safe  in  every 
respect. 

In  many  applications  of  the  needle-beam  scaffold 
one  of  the  beams  stands  higher  than  the  other,  so  that 
the  platform  planks  are  set  at  a  considerable  inclina- 
tion. Under  circumstances  of  this  kind  there  is  often 
serious  danger  of  the  planks  becoming  displaced  to  such 
an  extent  as  to  fall  from  the  needle-beams.  In  such  a 
case  the  workmen  may  also  fall,  or  the  planks,  in 
descending,  may  injure  other  persons  who  are  below. 
This  kind  of  an  accident  is  particularly  likely  to  occur 
when  the  men  on  the  scaffold  are  using  pneumatic 
"guns"  or  "jap  hammers",  the  jar  from  which  some- 
times causes  the  planks  to  crawl  into  dangerous  posi- 
tions in  the  course  of  time,  even  though  they  may  have 
been  correctly  placed  at  the  outset.  To  guard  against 
trouble  of  this  kind  it  is  best  to  bore  a  hole  through 
each  end  of  every  scaffold  plank,  and  to  slip  a  long  bolt 
through  every  hole.  In  order  to  prevent  the  bolt  from 
dropping  out  in  case  the  plank  is  turned  over,  it  should 
be  provided  with  a  tightly-fitting  nut,  which  should  be 
screwed  on  far  enough  to  avoid  all  danger  of  its  work- 
ing loose  and  becoming  lost,  but  not  too  far  to  per- 
mit the  bolt  to  act  as  an  effective  safety  stop,  which- 
ever side  of  the  plank  is  uppermost.  The  bolts  should 
be  placed  outside  of  the  needle-beams  in  all  cases,  so 
that  the  planks  cannot  slip  off  at  the  end.  Some  fore- 
men who  are  quite  willing  to  use  these  bolts  at  the 
upper  ends  of  the  planks  object  to  using  them  at  the 
lower  ends  also.  The  objection  that  is  urged  is  that  a 
bolt  at  the  lower  end  is  useless,  because  any  shifting  of 
the  plank  would  take  such  a  bolt  further  away  from 


PLASTERERS'  AND  DECORATORS'  SCAFFOLDS  277 

the  needle-beam,  instead  of  bringing  it  up  against  it. 
It  is  wise,  however,  to  use  the  bolts  at  both  ends,  be- 
cause when  they  are  used  at  only  one  end  the  workmen 
often  lay  the  planks  down  with  the  bolt  end  at  the  lower 
needle-beam,  and  in  this  case  the  object  of  the  device 
is  totally  defeated.  It  is  therefore  far  safer  to  put 
a  bolt  at  each  end  of  each  plank,  as  we  have 
recommended. 

When  the  planks  are  to  be  used  in  a  steeply-in- 
clined position,  they  should  be  provided  with  cleats  to 
afford  the  workmen  a  good  foothold,  as  described  in 
the  present  paragraph  or  in  paragraphs  143  and  144. 

146.  Plasterers'  and  Decorators'  Inside  Scaffolds. 
The  scaffolds  that  are  used  for  interior  work  by  plas- 
terers, painters,  and  decorators,  and  for  making  light  in- 
side repairs,  are  of  very  various  kinds.  When  it  is  not 
necessary  to  reach  high  places,  barrels  are  often  used  to 
support  the  planks  upon  which  the  men  stand.  These 
may  serve  the  purpose,  but  they  are  not  recommended 
because  they  frequently  collapse  while  in  use.  It  is  par- 
ticularly dangerous  to  stand  on  the  head  of  a  barrel, 
because  it  is  likely  to  give  way,  causing  the  man  stand- 
ing on  it  to  fall  upon  the  ends  of  the  staves,  often  with 
serious  results,  If  a  barrel  must  be  used,  a  plank 
should  be  laid  across  it,  from  edge  to  edge,  for  the 
workman  to  stand  on. 

It  is  immeasurably  better  and  safer  to  use  horses 
or  supports  of  other  forms,  upon  which  to  lay  the 
planks  that  constitute  the  working  platform.  Various 
special  devices  of  this  kind  are  shown  in  Fig.  107.  All 
supports,  whatever  their  nature,  should  be  strong  and 
sound.  Trestles  (or  "horses")  should  not  be  used 
more  than  two  tiers  high,  because  if  work  must  be 


278 


SCAFFOLDS  OF  OTHER  KINDS 


done  at  a  greater  elevation  than  can  be  reached  in  this 
way,  it  is  better  to  substitute  a  support  of  some  other 
kind.  Special  horses,  much  taller  than  the  ordinary 
builders'  horse,  are  often  used  when  it  is  necessary 
to  work  on  the  ceilings  or  upper  parts  of  rooms  of 
ordinary  height. 

If  it  is  necessary  to  increase  the  height  of  a  horse 
somewhat,  this  should  be  accomplished  by  nailing  on 
stout  strips  of  strong,  first-class  material,  and  not  by 
propping  up  the  horse  by  means  of  bricks  or  other  in- 
secure objects,  'nor  by  using  flimsy  material  that  is 
unsuited  to  the  purpose. 


FIG.  107.     LADDERS  AND  SCAFFOLDS  FOR  INTERIOR  WORK. 

(Exhibited  at  the  Leipzig  Architectural  Exposition,  1913.) 


PLASTERERS'  AND  DECORATORS'  SCAFFOLDS  279 

When  double  ladders,  hinged  together  at  the  top, 
are  used  for  supporting  platform  planks,  they  should 
be  designed  so  that  they  cannot  be  spread  to  more  than 
a  limited  distance,  and  they  should  be  opened  out  as 
widely  as  possible  before  the  planks  are  laid  on  them. 
Short  ladders  of  special  form,  leaning  against  walls,  are 
often  used  to  support  planks  for  decorators'  platforms. 
These  frequently  serve  well  enough,  but  they  should 
never  be  used  on  slippery  floors,  nor  should  they  be 
set,  under  any  circumstances,  at  an  angle  sufficiently 
oblique  to  make  slipping  at  the  foot  in  the  least  degree 
likely;  and  ladders  that  are  used  in  this  way  should 
preferably  be  provided  with  safety  shoes  or  spurs. 

English  authorities  recommend  that  the  planks  that 
are  used  as  platforms  in  connection  with  ladders,  steps, 
or  folding  trestles,  should  not  be  less  than  9  inches  wide 
and  11/2  inches  thick,  and  that  they  should  not  have 
a  span  exceeding  9  feet,  as  measured  between  supports. 
The  same  authorities  further  recommend  that  steps 
shall  not  be  used  for  supporting  platforms  that  are  more 
than  7  feet  in  height.  These  particular  regulations 
have  no  binding  force  in  the  United  States,  unless  they 
happen  to  be  specified,  here  and  there,  in  local  ordi- 
nances; but  they  are  nevertheless  sound,  and  it  is  ad- 
visable to  adopt  them  in  our  own  practice. 

When  the  work  that  is  to  be  done  is  situated  at  a 
level  that  cannot  be  safely  reached  by  such  methods  as 
we  have  described  above,  scaffolds  are  often  erected 
that  are  similar  in  general  design  to  the  independent 
pole  scaffold  considered  in  Section  IV  (page  83)  in  con- 
nection with  the  building  of  walls  from  the  outside.  The 
poles  and  ledgers  of  a  plasterers'  or  decorators'  pole 
scaffold  usually  run  in  both  directions,  however,  as 


280 


SCAFFOLDS  OF  OTHER  KINDS 


shown  in  Fig.  108,  because  the  scaffold  ordinarily 
occupies  the  entire  room ; — though  when  the  room  is  of 
vast  dimensions  it  may  be  left  open  in  the  center,  an 
independent  pole  scaffold  being  built  around  the  four 
walls,  while  the  ceiling  is  reached  from  a  suspended 
platform.  For  a  particularly  fine  example  of  the  last- 
named  type  of  construction  the  reader  may  refer  to  the 
frontispiece  of  this  volume,  which  shows  one  of  the 
largest  and  most  elaborate  scaffolds  ever  erected  for  the 
use  of  decorators  alone. 

Fig.  109  gives  an  approved  design,  for  ordinary 
heights,  of  a  plasterers'  pole  scaffold  of  the  type  of  con- 
struction shown  in  Fig.  108.  When  it  is  necessary  to 


FIG.  108.     INTERIOR  POLE  SCAFFOLD. 


PLASTERERS'  AND  DECORATORS'  SCAFFOLDS 


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282  SCAFFOLDS  OF  OTHER  KINDS 

extend  the  scaffold  to  an  unusual  height,  the  support- 
ing poles  should  be  made  larger.  The  same  general 
design  may  also  be  used  for  a  painters'  or  decorators' 
scaffold,  but  the  construction  may  then  be  somewhat 
lighter,  because  the  weight  to  be  supported  is  usually 
materially  less. 

Diagonal  bracing,  in  both  directions,  is  important 
in  connection  with  interior  scaffolds  of  this  type,  unless 
they  stand  practically  in  contact  with  the  walls  on  all 
four  sides.  Even  if  they  stand  away  from  the  walls 
somewhat  (as  they  do  in  most  cases),  the  necessary 
lateral  support  may  be  had,  if  desired,  by  thrusting  out 
stringers  or  struts  from  the  scaffold  to  the  walls  at  every 
outside  pole,  and  at  every  ledger-level.  If  this  con- 
struction is  objectionable  on  account  of  the  danger  of 
marring  the  walls,  the  ends  of  the  projecting  struts  or 
thrust -outs  may  be  padded.  As  a  rule,  however,  it  is 
important  to  keep  them  away  from  the  building  alto- 
gether, leaving  a  clear  interval  of  at  least  a  few  inches 
in  order  to  give  the  men  free  access  to  every  part  of 
the  wall  area;  and  in  such  cases  reliance  must  be  placed 
upon  the  diagonal  bracing  to  stiffen  the  structure 
against  vibration  and  deformation. 

In  splicing  the  poles  of  scaffolds  of  this  kind  the 
same  methods  are  to  be  followed  that  are  used  in  con- 
nection with  the  bricklayers'  pole  scaffold  described  in 
Section  III  (page  38).  The  same  care  should  also  be 
used  in  the  selection  of  material,  to  have  it  both  good 
in  quality  and  ample  in  size  and  quantity.  Care  should 
also  be  taken  to  have  the  poles  stand  truly  vertical, 
because  the  stresses  that  the  diagonal  braces  may  have 
to  sustain  will  be  materially  reduced  if  this  point 
receives  proper  attention. 


MISCELLANEOUS  SCAFFOLDS  283 

Certain  English  authorities  approve  of  spacing  the 
platform  planks  of  a  scaffold  of  this  kind  so  that  be- 
tween each  pair  of  planks  there  may  be  an  interval  not 
exceeding  seven  inches  in  width  (or  some  say  one  foot) , 
when  the  scaffold  is  supported  by  poles  and  is  con- 
structed inside  of  the  building.  A  similar  spacing  of 
the  planks  is  also  common  in  the  United  States,  but  it 
is  far  safer  to  plank  the  platforms  over  continuously 
and  tightly  wherever  they  are  needed,  and  at  other 
places  the  planks  may  be  omitted  entirely.  When 
spaces  amounting  to  from  several  inches  to  a  foot  are 
left  between  planks  there  is  not  much  danger  of  work- 
men falling  down  through  the  openings,  but  there  is 
always  serious  danger  of  tools  and  materials  falling 
down  and  striking  workmen  below,  and  many  acci- 
dents occur  in  this  way. 

147.  Miscellaneous  Scaffolds.  Many  of  the  scaf- 
folds that  are  described  in  this  book  in  connection 
with  special  kinds  of  work  are  also  used  with  little  or 
no  modification  for  work  of  other  kinds.  The  painters' 
swinging  scaffold,  for  example,  may  be  used  for  wash- 
ing down  a  building,  or  for  making  light  repairs. 
There  are  also  many  special  forms  of  scaffolds,  that  are 
used  for  special  purposes ;  but  we  cannot  undertake  to 
describe  them  all  here,  partly  because  a  full  description 
would  take  a  prohibitive  amount  of  space,  and  partly 
because  the  principles  upon  which  their  safety  depends 
have  already  been  sufficiently  discussed  in  connection 
with  scaffolds  of  other  kinds. 

In  building  or  repairing  factory  chimneys,  the  work 
is  done  sometimes  from  the  outside  and  sometimes  from 
within,  and  sometimes  from  both  sides  simultaneously. 
In  putting  up  a  pole  scaffold  around  the  outside  of  a 


284 


SCAFFOLDS  OF  OTHER  KINDS 


chimney,  careful  attention  should  be  paid  to  the  bracing, 
because  although  the  structure  cannot  well  pull  away 
from  the  chimney,  it  may  nevertheless  fall  down  by 
revolving  or  twisting  around  the  middle  line  of  the 
chimney  as  an  axis,  so  that  each  pole  falls  in  a  side- 
wise  or  tangential  direction.  In  repairing  factory  chim- 
neys it  is  often  necessary  for  a  man  to  climb  the  chim- 
ney, either  inside  or  outside.  For  this  purpose  it  is  best 
to  have  an  iron  ladder  permanently  secured  to  the  chim- 
ney, both  the  ladder  and  its  fastenings  being  so  strong 
that  there  will  be  no  danger  of  corrosion  or  other  forms 


FIG.  110.     PORTABLE  SCAFFOLD  FOR  LIGHT  WORK. 

(The  platform  is  securely  fastened  to  both  trestles.) 


MISCELLANEOUS  SCAFFOLDS  285 

of  deterioration  affecting  them  to  such  an  extent  as  to 
make  them  dangerous  to  climb.  When  there  is  no 
such  ladder,  iron  spikes  may  be  driven  into  the  chim- 
ney by  the  first  workman  as  he  climbs  up.  No  man 
should  be  permitted  to  undertake  a  task  of  this  kind 
unless  he  has  had  great  experience  in  working  at  high 
altitudes,  and  has  demonstrated  his  fitness  for  it;  and 
the  man  who  does  the  work  should  be  required  to 
attach  himself  securely,  by  the  aid  of  a  stout  life  line, 
to  each  spike  before  he  undertakes  to  drive  the  next 
one  above. 

Protection  should  be  provided  inside  of  chimneys 
as  well  as  outside,  when  the  men  are  to  work  within 
the  shaft,  to  guard  against  the  fall  of  tools  and 
materials  from  upper  levels  upon  persons  working 
below.  Platforms  are  often  supported  inside  of  chim- 
neys by  merely  resting  them  upon  offsets  of  the  brick- 
work within  the  shaft.  We  do  not  consider  this  to  be 
good  practice  unless  the  offsets  are  unusually  wide,  and 
even  in  that  case  the  platforms  should  be  arranged 
with  special  care,  so  that  it  will  be  impossible  for  any 
of  the  planks  to  slip  away  from  the  supporting  ledges 
and  fall  down. 

Iron  stacks,  which  have  to  be  painted  at  suitable 
intervals,  should  have  solid  iron  ladders  permanently 
attached  to  them,  as  already  described  in  connection 
with  chimneys.  When  such  ladders  are  provided,  every 
man  who  has  to  climb  them  should  be  furnished  with  a 
safety  belt,  attached  to  a  strong  hook  which  the  climber 
can  catch  over  the  rungs  of  the  ladder  as  he  pro- 
ceeds upward. 

When  an  iron  stack  has  no  ladder,  it  is  often  pro- 
vided with  a  pulley  at  the  top,  over  which  a  rope  runs, 


286 


SCAFFOLDS  OF  OTHER  KINDS 


after  the  manner  of  the  halliards  on  a  flagpole.  By 
means  of  this  rope  a  steel  cable  with  a  securely-attached 
hook  can  be  drawn  up,  so  that  the  hook  can  be  made 
fast  to  the  top  edge  of  the  stack.  When  this  method 
is  used,  no  workman  should  be  allowed  to  trust  his 
weight  upon  the  halliards  that  have  been  exposed  to  the 
weather.  These  should  be  used  merely  for  drawing  up 
the  cable  by  means  of  which  the  man  who  is  to  in- 
stall the  scaffold  is  to  be  raised. 

For  cleaning  buildings,  ''cradles"  are  often  used, 
similar  to  the  painters'  swinging  scaffold.  These  should 
be  of  sufficient  size  for  the  use  to  which  they  are  to  be 
put,  and  they  should  be  strongly  made,  and  provided 
with  stout  suspension  ropes  and  with  a  guard-rail 
and  foot -board  all  around. 

Whenever  scaffolds  suspended  by  ropes  are  used, 
whether  on  chimneys  or  on  any  other  kind  of  structure, 


FIG.   111.     FIXED  POLE  SCAFFOLD  FOR  LIGHT  WORK. 

(Note  the  bracing,  in  both  directions.) 


MISCELLANEOUS  SCAFFOLDS  287 

they  should  be  carefully  tested  (as  described  in  para- 
graph 144  in  connection  with  the  painters'  scaffold)  by 
raising  them  a  foot  or  two  above  the  ground,  and  then 
loading  them  with  a  weight  that  will  bring  upon  each 
rope  a  load  at  least  four  or  five  times  as  great  as  any 
stress  to  which  it  is  likely  to  be  subjected  during  the 
progress  of  the  work  for  which  the  scaffold  is  to  be  used. 
It  is  often  recommended  that  scaffolds  be  tested  in  this 
way  to  twice  the  load  they  are  to  carry,  but  we  do  not 
consider  it  sufficient  to  demonstrate  in  this  way  that  a 
scaffold  has  a  factor  of  safety  of  two,  under  a  dead  load. 
A  moving  load,  such  as  may  be  caused  by  a  sudden 
change  in  the  position  of  the  men  or  by  the  fall  of  one 
or  more  of  them  upon  the  scaffold  platform,  might 
easily  strain  the  suspending  ropes  to  twice  the  stress 
to  which  they  are  normally  subjected  by  the  equiva- 
lent dead  weight ;  and  hence  we  feel  that  a  factor  of  at 
least  four  or  five  should  be  employed  in  applying  the 
test  load. 

Roofers'  scaffolds,  for  use  in  laying  roofing  of  cor- 
rugated iron  or  other  similar  material,  should  have  plat- 
forms approximately  parallel  to  the  slope  of  the  roof, 
and  hung  at  a  convenient  distance  below  the  roof  by 
means  of  wire-rope  slings.  These  scaffolds  should  not 
be  used  for  supporting  any  weight  except  that  of  the 
men  themselves.  The  platforms  should  be  provided 
with  heavy  cleats  spaced  at  intervals  of  not  more  than 
10  inches  or  one  foot,  and  the  planks  should  be  secured 
in  some  very  positive  way,  so  that  they  cannot  slip  off 
of  the  bearer-bars  (or  ' 'needle-beams")  on  which  they 
rest  and  by  which  they  are  supported.  (For  further 
suggestions  applicable  to  scaffolds  of  this  kind,  the 
reader  should  refer  to  page  272,  paragraph  145.)  It 


288 


SCAFFOLDS  OF  OTHER  KINDS 


FIG.  112.     A  BOATSWAIN'S  CHAIR. 

(Courtesy  of  Illinois  Steel  Company.) 


MISCELLANEOUS  SCAFFOLDS 


289 


FIG.  113.     ANOTHER  FORM  OF  BOATSWAIN'S  CHAIR. 

(Note  the  stirrups,  and  the  knots  in  the  suspension  rope.) 

would  be  well  to  have  catch-nets  suspended  by  some 
independent  means  below  the  needle-beam  scaffolds 
used  by  roofers,  to  prevent  the  men  from  falling  to  the 
ground  in  case  of  accident ;  but  this  would  be  so  marked 
an  innovation  that  it  is  doubtful  if  we  can  hope  for  any 
widespread  adoption  of  the  idea  in  the  near  future. 

The  ' 'boatswain's  chair"  can  hardly  be  called  a 
scaffold,  but  it  may  be  merttioned  appropriately  in  this 
place  because  it  is  widely  used  for  painting  and  clean- 
ing, and  for  other  small  operations  which  can  be  per- 
formed by  one  man,  and  in  which  no  considerable 


290  SCAFFOLDS  OF  OTHER  KINDS 

amount  of  material  has  to  be  handled.  It  consists  of 
a  seat,  attached  by  means  of  a  sling  to  a  suspension 
rope.  The  suspension  rope  sometimes  passes  through 
a  block  overhead,  as  in  Fig.  112,  and  it  is  sometimes 
made  fast  to  a  fixed  object  above,  as  in  Fig.  113.  It 
may  also  be  secured  to  a  pole  by  means  of  a  suitable 
hitch  just  above  the  chair,  as  in  Fig.  114.  The  last- 
mentioned  method  is  often  used  in  painting  flagpoles 
and  other  similar  objects,  when  no  adequate  provision 
has  been  made  for  hoisting  the  workman  by  other  means ; 
but  it  is  not  recommended  if  either  of  the  other  two 
methods  can  be  safely  applied.  When  the  chair  is  sus- 
pended by  means  of  a  rope  passing  through  an  over- 
head block,  it  is  safest  to  have  the  free  end  of  the  rope 
secured  to  some  fixed  and  easily  accessible  object,  and 
to  have  the  chair  raised  and  lowered  by  two  or  more 
helpers.  If  this  is  not  practicable,  however,  the  work- 
man in  the  chair  may  do  the  raising  and  lowering  him- 
self, if  a  safe  and  suitable  method  of  fastening  the  free 
end  of  the  rope  has  been  provided  at  the  chair.  When 
the  suspension  rope  is  attached  to  a  fixed  point  over- 
head as  in  Fig.  113,  or  is  secured  to  a  pole  by  means  of 
a  hitch  as  in  Fig.  114,  it  is  important  to  provide  the 
workman  with  stirrups  upon  which  he  can  rest  his 
weight  while  he  is  shifting  the  hitch  by  which  the  chair 
is  made  fast.  In  any  such  case  the  stirrups  must  be 
supported  independently,  and  with  the  same  care  as 
the  chair  itself.  Whenever  practicable,  the  tools  and 
materials  required  by  the  workman  using  the  chair 
should  be  delivered  to  him  in  a  bucket  or  basket  by  a 
helper,  as  shown  in  Fig.  113.  In  every  case,  too,  the 
man  in  the  chair  should  wear  a  strong  safety  belt,  se- 
cured to  the  supporting  tackle  in  such  a  way  that  he 


MISCELLANEOUS  SCAFFOLDS 


291 


I 


,^ 

"T 


FIG.  114.     A  BOATSWAIN'S  CHAIR  ox  A  FLAGSTAFF. 

(Note  the  independent  stirrup,  on  which  the  workman  rests  his  weight  while  shifting 
the  position  of  the  chair.) 


292  SCAFFOLDS  OF  OTHER  KINDS 

will  be  safe  even  if  he  should  fall  from  the  chair.  The 
suspension  rope  should  be  first-class  in  quality,  and 
should  be  tested,  before  use,  with  a  load  at  least  four 
times  as  great  as  it  will  have  to  sustain  while  in  service. 
It  should  also  be  carefully  protected  against  exposure  to 
acid,  or  to  heat  that  might  conceivably  char  or  other- 
wise damage  it,  or  to  any  other  recognized  cause  of 
deterioration. 


XII.     STRUCTURES  SIMILAR  TO  SCAFFOLDS. 

148.  Sidewalk  Protection.  In  putting  up  a 
building  fronting  on  a  city  sidewalk  it  is  highly  im- 
portant to  provide  proper  protection  to  pedestrians  and 
others  who  have  to  use  the  sidewalk  or  street.  For 
this  reason  it  is  necessary  to  build  over  the  sidewalk  a 
protective  structure  that  will  be  strong  enough  to  pre- 
vent accident  from  any  material  that  may  fall.  This 
structure  is  sometimes  called  a  ''sidewalk  shed"  and 
sometimes  a  "sidewalk  bridge."  The  former  name  is 
preferable,  because  it  refers  to  the  protective  value  of 
the  structure.  The  name  "bridge"  is  given  in  reference 
to  the  fact  that  in  construction  work  it  is  often  neces- 
sary to  temporarily  remove  the  sidewalk,  or  some  part 
of  it,  and  it  then  becomes  important  to  bridge  over  the 
gaps  that  are  left,  in  order  that  travel  may  not  be  inter- 
rupted. The  sidewalk  shed,  as  usually  constructed, 
serves  both  of  these  purposes,  because  it  is  both  a  shed 
and  a  bridge. 

The  design  of  the  shed  will  naturally  depend  large- 
ly upon  the  conditions  to  be  met.  It  sometimes  hap- 
pens that  if  no  material  of  considerable  weight  is  to  be 
handled,  a  shed  of  light  construction  is  sufficient ;  but 
in  case  it  is  necessary  to  deal  with  heavy  materials, 
such  as  beams  and  blocks' of  stone,  the  shed  should 
be  of  exceedingly  stout  construction. 

The  accompanying  diagram  (Fig.  115),  which  rep- 
resents a  shed  that  was  used  during  the  erection  of  the 


294 


STRUCTURES  SIMILAR  TO  SCAFFOLDS 


SIDEWALK  PROTECTION  295 

Home  Office  building  of  THE  TRAVELERS  INSURANCE 
COMPANY,  shows  a  good  general  form  of  construction 
that  is  recommended  when  heavy  work  has  to  be 
handled.  No  attempt  is  here  made  to  show  the  bridge 
structure  by  which  the  shed  was  supported  from  below, 
as  it  was  thought  best  to  fix  attention  on  the  part  of 
the  shed  relating  to  the  protection  of  the  sidewalk. 

The  shed  rested  upon  two  stout  sills,  AA,  which 
were  supported  by  the  bridgework  to  which  we  have 
referred.  Across  these  sills  lay  others,  BB,  spaced  at 
intervals  of  about  eight  feet,  and  upon  these  rested  the 
vertical  posts  CC.  Running  over  the  tops  of  these 
posts,  and  resting  upon  them,  were  other  horizontal 
sills  DD,  which  in  turn  supported  heavy  cross  stringers, 
FF,  which  were  of  the  same  size  as  the  lower  stringers, 
BB,  but  twice  as  numerous. 

To  stiffen  the  structure  in  a  lengthwise  direction, 
diagonal  braces  were  erected,  as  shown  at  EE,  and  to 
give  it  similar  support  for  resisting  deformation  or  dis- 
placement sidewise,  similar  diagonal  braces,  HHy  were 
provided. 

Over  the  stringers,  FF,  there  was  laid  a  flat,  hori- 
zontal roof,  J.  composed  of  stout  spruce  planks  laid 
closely  together.  At  the  street  margin  of  this  plank 
flooring  a  strong  high  framework,  K,  was  erected  and 
made  fast  to  the  stringers,  FF.  This  frame  was  covered 
with  strong,  close-meshed  wire  netting. 

The  shed  was  provided  with  a  plank  flooring,  L, 
which  was  protected  on  the  street  side  by  a  stout  guard- 
railing,  N,  provided  with  '  a  foot-board  and  strongly 
braced  as  shown.  At  the  inner  side  of  the  shed,  toward 
the  building,  a  high  plank  partition,  M,  was  erected  to 
protect  passers  from  exposure  to  hazard  of  any  kind. 


296 


STRUCTURES  SIMILAR  TO  SCAFFOLDS 


The  planks  composing  this  partition  were  also  set  close 
together,  and  rested  in  contact  with  the  floor  planks,  L. 

For  the  protection  of  passers  against  rain  and 
melting  snow,  a  corrugated-iron  roof,  5,  was  provided. 
This  was  set  at  a  proper  inclination  to  shed  water  free- 
ly, and  was  located  immediately  below  the  cross-beams 
FF.  It  was  supported  upon  the  longitudinal  stringers 
shown  at  R,  which  were  themselves  supported  by  in- 
clined cross-pieces,  PP. 

Sidewalk  sheds  are  often  used  for  the  storage  of 
materials,  and  to  a  certain  extent  this  is  necessary; 
but  extreme  care  should  be  taken  to  see  that  they  are 
not  loaded  beyond  their  safe  capacity,  after  making 
allowance  for  a  large  factor  of  safety.  The  man  in 


FIG.   116.     ORNAMENTAL  SIDEWALK  SHED  IN  NEW  YORK  CITY. 


SIDEWALK  PROTECTION 


297 


FIG.  117.     A  VERY  ARTISTIC  SIDEWALK  SHED. 


298 


STRUCTURES  SIMILAR  TO  SCAFFOLDS 


charge  of  the  work  should  see  to  this  personally,  be- 
cause if  he  does  not  do  so  the  workmen  are  likely  to 
go  on  depositing  more  material  on  the  roof  of  the  shed 
after  it  is  already  loaded  to  its  safe  limit,  since  it  is  a 
convenient  place  for  such  storage. 

Another  point  to  which  attention  should  be  called 
in  this  place  is  the  location  of  the  contractor's  office. 
This  is  usually  placed  somewhere  on  the  roof  of  the 
bridge,  and  for  some  incomprehensible  reason,  or  per- 
haps for  no  reason  at  all,  it  is  commonly  located  in  an 
unnecessarily  dangerous  position.  Whenever  there  is  a 
choice  of  location,  this  office  should  be  placed  where  it 
will  be  least  exposed  to  accident  from  falling  material. 


FIG.  118.     AN  EXCEEDINGLY  ORNATE  SIDEWALK  SHED, 


CATCH-SCAFFOLDS  AND  PLATFORMS  299 

In  recent  years  there  has  been  a  movement  in 
favor  of  making  sidewalk  sheds  more  or  less  ornamen- 
tal, and  in  a  few  of  our  larger  cities  local  municipal  art 
societies  have  interested  themselves  in  this  movement 
in  the  belief  that  there  is  no  reason  why  a  bridge  of 
ugly  appearance  should  be  erected  on  a  public  street, 
if  the  contractor  is  willing  to  provide  one  of  more 
seemly  appearance.  Figs.  116,  117,  and  118  show 
bridges  in  which  an  attempt  at  ornamentation  has 
been  successfully  carried  out.  Attention  is  particularly 
directed  to  the  bridge  shown  in  Fig.  118,  wrhich  is  orna- 
mented, as  will  be  seen,  with  flowering  plants  and  also 
with  shrubs  set  in  tubs.  The  ornamentation  of  side- 
walk sheds  is  commendable,  but  it  should  never  be 
overlooked  that  the  strength  and  safety  of  the  shed 
should  always  be  the  first  consideration,  and  no  thought 
should  be  given  to  ornamentation  of  any  kind  until 
safety  has  been  absolutely  assured. 

149.  Catch-scaffolds  and  Platforms.  We  have 
already  referred,  in  paragraph  75,  to  the  importance  of 
providing  protection  over  passageways  and  workplaces, 
to  prevent  workmen  and  other  persons  from  being  in- 
jured by  the  fall  of  material  from  scaffolds  above. 
When  the  scaffolds  are  high  the  importance  of  protec- 
tion is  very  much  greater,  and  the  protection  in  such 
cases  should  be  correspondingly  more  complete.  It 
should  also  be  arranged  with  reference,  not  only  to  the 
passages  and  workplaces  that  may  be  below,  but  also 
to  sidewalks,  streets,  and  the  ground  level  in  general. 
Sometimes  sufficient  protection  may  be  had  by  means 
of  a  thrust -out  scaffold  that  is  confined  to  some  par- 
ticular part  of  the  building,  where  the  hazard  is  greatest. 
Catch-scaffolds  of  this  kind  are  shown  in  Fig.  119. 


300 


STRUCTURES  SIMILAR  TO  SCAFFOLDS 


liN& 


::::::: 


FIG.    119.     SHOWING   CATCH-SCAFFOLDS    FOR   PROTECTING    THE 
SIDEWALKS  AND  STREETS  FROM  FALLING  OBJECTS. 


CATCH-SCAFFOLDS  AND  PLATFORMS  301 

High  up  on  the  building  in  the  foreground  two  such 
scaffolds  may  be  seen,  and  in  the  rear  another  is  shown 
that  extends  along  the  entire  side  of  the  building.  It 
is  important  in  platforms  of  this  kind  to  provide  the 
outer  edge  with  a  stout  board  fence,  or  with  a  strong 
screen  of  close-meshed  wire  netting. 

In  the  erection  of  the  Woolworth  Building  in  New 
York  City  special  attention  was  given  to  the  construc- 
tion of  catch -scaffolds  of  this  kind,  and  platforms  20 
feet  wide  were  thrust  out  from  the  building  at  four  dif- 
ferent heights.  These  had  wire-mesh  screens  arranged 
along  their  outer  edges  to  give  still  further  protection. 
Fig.  120  shows  three  of  these  platforms,  and  Fig.  121 
shows  the  appearance  of  the  platform  at  the  fifteenth 
floor,  which  is  the  lowest  one  of  those  shown  in  Fig.  120. 
The  amount  of  debris  on  the  floor  of  this  platform 
should  be  especially  noted.  Some  of  the  fragments 
would  have  produced  very  serious  injuries  if  they  had 
struck  persons  below. 

The  wire  netting  at  the  edge  is  not  supposed  to  be 
relied  upon  for  checking  the  direct  fall  of  materials, 
but  after  they  have  struck  the  main  platform  they 
often  rebound  somewhat,  and  the  netting  is  useful  in 
preventing  such  fragments  from  bounding  or  rolling 
over  the  edge  of  the  platform. 

We  have  referred,  in  paragraph  143,  to  the  advisa- 
bility of  having  platforms  for  preventing  the  fall  of  men 
who  are  engaged  in  work  upon  steep  roofs,  and  the 
counsel  that  is  there  given  will  of  course  apply  with 
such  modifications  as  may  be  necessary  to  other  con- 
ditions where  similar  hazards  prevail. 

It  has  often  been  urged  that  in  the  case  of  a  pole 
scaffold  a  fully  planked  platform  should  be  left  a  short 


302 


STRUCTURES  SIMILAR  TO  SCAFFOLDS 


distance  below  the  one  on  which  the  men  are  working, 
so  that  in  the  event  of  failure  of  the  upper  platform 
the  men  would  fall  only  a  short  distance.  Authorities 


FIG.    120.     CATCH-SCAFFOLDS  ON  THE    WOOLWORTH    BUILDING. 


CATCH-SCAFFOLDS  AND  PLATFORMS 


303 


who  have  given  attention  to  the  subject  of  safety  in 
connection  with  building  construction  are  divided 
among  themselve's  with  regard  to  the  advisability  of 


FIG.   121.     SHOWING  ONE  OF  THE  PLATFORMS  OF  FIG.  120. 


304  STRUCTURES  SIMILAR  TO  SCAFFOLDS 

adopting  this  plan.  There  can  be  no  doubt  that  it  is 
a  wise  precaution  if  the  builder  is  willing  to  go  to  the 
expense  that  is  involved  (which  may  often  be  confined 
to  the  furnishing  of  extra  platform  planks  and  the 
doing  of  a  little  more  work) ,  and  if  the  extra  platform 
is  also  put  up  in  such  a  way  that  it  does  not  interfere 
with  the  proper  bracing  and  staying  of  the  scaffold 
as  a  whole.  In  scaffolds  of  the  independent  pole  type 
(such  as  are  discussed  in  Section  IV,  page  83)  a  num- 
ber of  platforms  are  often  necessary,  either  for  the  stor- 
age of  material  in  reasonable  amounts,  or  for  the  carry- 
ing on  of  the  work;  and  in  such  cases  the  auxiliary 
platforms  that  are  required  for  these  reasons,  serve 
also  as  catch-platforms  to  check  the  fall  of  the  men  in 
the  event  of  failure  of  the  topmost  platform. 

150.  Material  Hoists.  In  the  present  section  we 
shall  refer  merely  to  the  construction  of  these  hoists, 
and  shall  not  discuss  the  operation  of  them.  There  are 
many  important  questions  relating  to  signals,  guard- 
ing, and  other  matters,  to  which  it  is  important  to  give 
careful  attention  in  order  to  insure  safety ;  but  these  are 
too  far  removed  from  the  general  subject  of  scaffolds 
to  be  appropriately  treated  in  this  volume. 

Hoists  that  are  built  inside  the  building,  and  con- 
structed and  operated  similarly  to  ordinary  freight  or 
passenger  elevators,  call  for  no  special  mention  here. 
It  is  only  when  they  are  built  in  the  form  of  separate 
structures  (usually  external  to  the  building) ,  that  they 
are  appropriate  subjects  for  consideration  in  a  book 
that  is  confined  to  scaffolding  and  closely  allied  struc- 
tures. When  so  built,  the  hoists  usually  take  the  form 
of  towers,  and  they  must  be  constructed  so  that  they 
will  have  the  necessary  strength  and  stiffness  to  sustain 


MATERIAL  HOISTS 


305 


FIG.  122.     A  PAIR  OF  MATERIAL  HOISTS. 


306  STRUCTURES  SIMILAR  TO  SCAFFOLDS 

all  the  various  stresses  to  which  they  may  be  subjected. 
Such  towers  should  be  built  of  sound  material,  and 
should  be  designed  and  erected  with  careful  regard  to 
the  maximum  loads  they  may  have  to  carry.  They 
should  be  strongly  cross-braced  and  strutted,  and 
should  have  exceedingly  firm  and  solid  foundations. 
Great  care  should  also  be  taken  to  see  that  they 
are  made  secure  against  overturning  in  any  direction. 
With  this  in  view,  they  should  be  safely  guyed,  or 
strongly  anchored  to  the  building  itself,  or  fixed  solidly 
in  some  other  effective  way.  When  used  in  connection 
with  a  high  building,  they  should  not  be  run  up  to  their 
ultimate  height  at  the  outset,  because  if  this  is  done 
the  problem  of  keeping  them  safely  in  position  is  often 
serious,  until  the  framework  of  the  building  has  risen 
to  a  considerable  elevation.  In  such  cases  it  is  better 
to  limit  the  hoist-towers,  at  first,  to  an  altitude  that 
will  suffice  for  immediate  needs,  and  to  extend  them 
upward  when  the  work  has  proceeded  far  enough  to 
make  it  feasible  to  provide  a  safe  support  by  bracing 
their  lower  parts  to  the  framework  of  the  building. 
Care  should  be  taken  to  have  all  towers  of  this  kind 
truly  straight  and  vertical,  so  that  the  uprights  that 
sustain  the  loads  will  not  be  exposed  to  bending  stresses, 
and  so  that  the  guys  or  other  supports  that  are  pro- 
vided will  not  be  subjected  to  stresses  of  unnecessary 
severity.  In  Fig.  122,  which  shows  a  pair  of  material 
hoists  of  the  kind  here  under  consideration,  it  will  be 
particularly  noticed  that  the  two  towers  are  fastened 
together  in  several  places,  both  by  horizontal  stringers 
and  by  diagonal  braces.  They  are  also  secured  to  the 
building  at  three  different  heights,  by  beams  that  pass 
in  through  the  window  openings  in  such  a  manner  that 


MATERIAL  HOISTS  307 

they  will  not  interfere  with  the  progress  of  the  work. 

Hoistways  of  this  kind  are  often  sheathed  with 
boards,  and  where  this  is  done  it  is  best  to  cover  them 
on  the  inside,  because  a  smoother  surface  is  thereby 
presented  to  the  moving  material,  and  loads  are  less 
likely  to  catch  against  projections  in  the  shaftways. 
Long  pieces  of  material,  when  placed  endwise  on  the 
cage  or  platform  of  a  hoist,  sometimes  give  serious 
trouble  in  this  way ;  and  boxes  and  other  objects  that 
are  placed  too  near  the  edge  of  the  platform  often  be- 
come displaced  so  that  they  catch  on  the  framework  of 
the  hoistway.  The  method  of  sheathing  here  recom- 
mended is  seldom  followed  in  practice,  the  sheathing 
being  usually  put  on  the  outside  of  the  framework. 
There  is  apparently  no  good  reason  for  doing  this,  how- 
ever, except  that  the  hoistway  looks  a  little  better  from 
the  outside,  and  that  it  is  somewhat  easier  to  handle 
the  sheathing  in  putting  it  on.  Aside  from  the  small 
amount  of  extra  work  that  may  be  required  in  the  con- 
struction, the  only  objection  that  can  be  offered  against 
placing  the  sheathing  on  the  inside  as  we  recommend, 
is  that  by  so  doing  it  becomes  necessary  to  have  the 
hoistway  two  or  three  inches  larger,  each  way. 

Some  forms  of  scaffold -like  structures  that  are  used 
in  connection  with  hoisting  have  elevated  platforms 
upon  which  men  must  stand  or  work.  All  platforms 
of  this  kind  should  be  ample  in  size,  and  they  should  be 
closely  planked  over,  and  provided  with  guard-rails, 
foot -boards,  and  netting,  as  described  in  paragraph  130 
in  connection  with  suspended  scaffolds  for  construction 
work.  Safe  means  of  access  to  these  platforms  should 
also  be  provided.  Stairways  are  greatly  to  be  pre- 
ferred for  this  purpose,  although  runways  or  ladders 


308 


STRUCTURES  SIMILAR  TO  SCAFFOLDS 


may  also  be  satisfactory   if   they    are    properly  con- 
structed, guarded,  and  secured. 

Fig.  123  shows  a  form  of  hoisting  scaffold  that  is 
used  to  a  considerable  extent  in  Germany,  especially  in 


FIG.  123.    A  GERMAN  MATERIAL  HOIST. 


ARCH  CENTERS  AND  OTHER  FALSE  WORK  309 

connection  with  the  erection  of  stone  buildings.  The 
wall  that  was  being  laid  in  this  particular  case  was 
parallel  with  the  street,  and  located  just  back  of  the 
sidewalk  shed.  It  cannot  be  seen  in  the  engraving, 
except  in  one  small  section  just  above  the  level  of  the 
top  of  the  shed  at  the  extreme  left.  The  framework 
was  thoroughly  braced  in  both  directions,  and  the  braces 
and  other  parts  were  fastened  together  by  bolts  of 
generous  size.  Along  each  side  of  the  structure,  at  the 
top,  there  was  a  platform  with  a  hand-rail  and  foot- 
board, and  a  track  was  also  provided,  along  which  a 
hoisting  machine  traveled  so  that  it  could  be  used  at 
any  point  to  raise  a  stone  to  its  proper  position  upon  the 
wall.  A  hoist  of  this  kind,  in  its  construction  and  opera- 
tion, closely  resembles  a  temporary  traveling  crane. 

Other  crane-like  forms  of  hoists  are  used  in  con- 
nection with  the  raising  of  material  for  building  opera- 
tions, but  we  shall  not  discuss  them  in  this  work  be- 
cause they  can  hardly  be  included  under  the  general 
heading  of  scaffolds. 

Whatever  the  method  that  is  used  for  raising  the 
materials,  all  persons  should  keep  from  under  loads 
that  are  being  hoisted,  or  that  are  suspended  in  the  air; 
and  stones,  bricks,  tools,  and  other  materials  should 
always  be  handled  by  safe  methods.  Small  objects 
may  be  placed  in  buckets  or  other  similar  receptacles, 
and  when  slings  are  used  they  should  be  employed  only 
in  connection  with  objects  for  the  handling  of  which 
they  are  adapted. 

151.  Arch  Centers  and  Other  False  Work.  All 
work  of  this  kind  should  be  erected  and  supervised 
under  the  direction  of  a  designated  man  who  thoroughly 
understands  the  subject  and  its  dangers.  The  false 


310 


STRUCTURES  SIMILAR  TO  SCAFFOLDS 


centers  that  are  used  in  the  construction  of  arches 
should  be  made  particularly  strong,  because  they  are 
often  loaded  very  heavily.  They  should  also  be  solidly 
supported  from  below,  so  that  they  cannot  sink  under 
the  weight  to  which  they  are  subjected,  and  they  should 
be  effectively  braced  or  shored  so  that  they  cannot  fall 
over  sidewise.  False  centers  should  be  held  in  position 
by  wedges  or  in  some  other  equivalent  way,  so  that  they 
can  be  removed  without  straining  the  structure  that 


FIG.  124.     FALSE  WORK  FOR  SUPPORTING  A  STONE  ARCH. 


ARCH  CENTERS  AND  OTHER  FALSE  WORK  311 

they  have  supported,  and  without  communicating 
shocks  to  it, — the  wredges  being  carefully  backed  out 
before  the  centers  are  otherwise  disturbed. 

Arch  centers  should  never  be  removed  until  the 
cement,  mortar,  or  concrete  is  thoroughly  set,  nor  until 
the  abutments  are  heavy  enough  and  strong  enough  to 
withstand  the  thrust  of  the  arch  with  entire  safety. 


XIII.     GENERAL  COUNSEL. 

152.  Introductory.     The    present    section,    being 
devoted  to  counsel  with  regard  to  scaffolds  in  general, 
is  to  a  certain  extent  a  review  of  those  parts  of  the  pre- 
ceding  sections   that    relate   to   the   management    of 
scaffolds  and  of  the  workmen  who  build  them  and  use 
them.     More   or   less   repetition   of   matter   that   has 
already   been   given   in   earlier  parts   of  the  book  is 
therefore  inevitable.      The  section   is   far   more  than 
a   mere    review,    however,    because    it    also    contains 
many  suggestions  that  were  omitted  from  earlier  pages, 
or  that  were  passed  over  with  little  more  than  a  bare 
mention. 

153.  Construction    and    Material.     One    of    the 
most  important  duties  of  a  contractor  or  other  em- 
ployer, in  connection  with  the  erection  of  a  scaffold, 
is  to  see  that  the  work  is  done  under  the  immediate 
personal  supervision  of  a  man  who  thoroughly  under- 
stands the  dangers  that  are  involved,  and  who  knows 
what  precautions  should  be  taken  to   insure  safety. 
It   is  just   as  necessary  to  employ   experienced   and 
careful  men  in  building  scaffolds  as  in  building  more 
permanent    structures;     but    any    observant    person, 
by  merely   looking  with   critical  eye   at  the  various 
scaffolds  that  he  passes  in  his  daily  life,  can  see  that 
a  large  proportion  of  them  are  built  by  men  who  have 
no  special  training  or  fitness  for  the  work,  and  who 
are  either  unaware  of  the  dangers  to  which  the  work- 


CONSTRUCTION  AND  MATERIAL  313 

men  are  exposed,  or  unwilling  to  take  a  little  more 
time  and  trouble  in  order  to  eliminate  these  dangers. 

An  English  committee  that  gave  considerable 
attention  to  scaffold  hazards  a  few  years  ago  made 
the  following  suggestion,  in  which  we  heartily  concur: 
"It  would  be  a  great  boon  to  all  concerned  if  some 
means  were  devised  to  educate  workmen  in  the  skilful 
construction  of  scaffolding,  and  the  attention  of 
authorities  engaged  upon  technical  education  might 
(profitably)  be  drawn  to  the  desirability  of  offering 
evening-school  instruction  in  regard  to  this,  with 
practical  demonstrations".  The  instruction  should  not 
be  confined  to  evening  schools,  however.  In  our 
opinion  it  should  be  given  in  all  institutions  devoted 
to  technical  education. 

One  of  the  commonest  errors  in  scaffold  construc- 
tion consists  in  using  inferior  material,  and  using  it 
in  insufficient  amount.  Nothing  but  the  best  and 
strongest  material  should  be  employed,  and  it  should 
be  provided,  and  used,  in  generous  quantities.  The 
man  who  is  in  charge  of  the  erection  of  the  scaffold 
should  be  held  strictly  responsible  for  any  short- 
comings in  either  respect,  and  he  should  remember  that 
although  economy  of  material  is  commendable  in 
most  places,  it  should  be  the  very  last  consideration 
when  putting  up  a  scaffold. 

Spruce  is  strongly  recommended  for  most  of  the 
wooden  parts  of  scaffolds,  though  long-leaf  yellow  pine  is 
also  satisfactory  when  it  is  of  really  first-class  quality. 

Scaffold  practice  in  the  United  States  differs  from 
that  in  other  countries  in  many  respects.  For  example, 
the  suspended  scaffolds  that  are  described  in  Section 
X  (page  168),  and  which  are  used  so  generally  in  the 


314  GENERAL  COUNSEL 

construction  of  high  buildings  in  this  country  and  in 
Canada,  are  almost  unknown  elsewhere.  There  are 
many  minor  differences  in  practice,  also.  In  England, 
for  example,  the  putlogs  of  bricklayers'  pole  scaffolds 
are  supposed  to  be  securely  fastened  in  place,  whereas 
in  the  United  States  it  is  customary  to  rely  upon  the 
weight  of  the  platform  and  its  load  to  keep  the  put- 
logs from  shifting  their  positions,  and  there  are  few 
accidents  that  can  be  attributed  to  our  omission  of 
the  fastenings,  when  the  scaffold  is  built  in  accordance 
with  the  standards  advocated  in  this  book,  inspected 
at  proper  intervals  by  competent  men,  and  thor- 
oughly protected  against  accidental  shocks  and  other 
disturbances.  When  a  putlog  is  first  laid,  in  the  brick- 
layers' pole  scaffold,  the  wall  where  it  rests  is  "green"  ;— 
that  is,  the  mortar  is  still  soft.  Hence  the  adjoining 
bricks  would  be  likely  to  be  displaced  by  driving  wedges 
for  the  purpose  of  securing  the  putlog  in  its  hole,  and 
the  wedges  would  not  hold  well.  Moreover,  a  pull  on 
the  putlog  that  would  be  sufficient  to  overcome  the 
friction  between  the  putlog  and  the  wall  would  be  likely, 
when  the  wall  is  "green",  to  pull  one  or  more  bricks 
away  with  it  if  w^edges  were  used,  and  therefore  little 
or  nothing  would  be  gained.  It  is  safest  to  pay  careful 
attention  to  the  bracing  by  which  the  scaffold  is  tied 
to  the  building,  distributing  this  well  and  making  it 
amply  strong,  so  that  endwise  stresses  on  the  putlogs 
may  be  wholly  avoided. 

Nothing  should  be  done  hurriedly  in  erecting  a 
scaffold,  and  makeshifts,  either  in  materials  or  in 
methods,  should  never  be  adopted  or  permitted. 
Everything  about  the  job  should  be  done  in  the  safest 
way  possible,  and  all  superintendents  and  foremen 


THE  HUMAN  ELEMENT  315 

should  be  specially  and  definitely  instructed  to  take 
every  precaution  that  appears  to  be  needful  for  the 
prevention  of  accidents. 

In  using  suspended  scaffolds  of  the  overhead  type 
(see  page  194)  it  is  wise  to  have  a  man  watch  the 
machines,  to  prevent  the  cables  from  ''riding",  as 
described  in  paragraph  116.  When  this  tendency  is 
first  observed  it  can  often  be  effectively  checked  by 
pushing  the  cable  into  its  proper  position  by  means  of 
a  stout  stick. 

The  attention  of  a  man  engaged  in  erecting  a 
scaffold  should  never  be  drawn  away  from  his  work, 
even  momentarily.  There  may  appear  to  be  no  harm 
in  consulting  him  upon  some  other  matter,  or  in  obtain- 
ing his  assistance,  temporarily,  on  some  other  job; 
but  if  he  is  disturbed  in  this  way  he  is  likely  to  forget 
some  important  thing,  and  leave  some  part  of  the 
scaffold  in  an  unfinished  and  dangerous  state. 

154.  The  Human  Element.  Every  person  who 
wishes  to  make  use  of  a  scaffold  should  be  required 
to  satisfy  himself  of  its  safety,  before  venturing  upon  it. 
This  condition  should  be  strictly  enforced  with  respect 
to  every  individual  workman,  and  no  workman  who 
is  not  so  satisfied  should  be  required  to  use  the  scaffold, 
nor  should  he  be  penalized  in  any  way  on  account  of 
his  refusal. 

Foremen  should  assure  themselves  that  there  is 
no  ill  feeling  among  men  who  have  to  work  together 
under  conditions  in  which  friendly  co-operation  is 
essential  to  safety.  This  counsel  applies  not  only 
to  individual  workmen,  but  also,  and  perhaps  with 
greater  cogency,  to  cases  in  which  two  or  more  gangs 
of  men,  engaged  upon  different  parts  of  the  job,  have 


316  GENERAL  COUNSEL 

to  work  together.  Instances  could  be  cited  in  which 
feeling  has  run  so  high,  between  gangs  of  men  working 
on  the  same  job  but  having  different  interests  at 
stake,  that  open  hostilities  have  broken  out,  high 
up  on  the  framework  or  scaffolding  of  a  building, 
with  very  serious  results. 

Workmen  who  suffer  from  nervous  ailments,  or 
who  are  subject  to  dizziness  or  to  attacks  of  faintness, 
or  who  are  partially  deaf,  or  near-sighted  in  any 
important  degree,  or  who  suffer  from  rheumatism 
or  any  other  affliction  that  might  impair  their  activity 
of  mind  or  body,  should  give  notice  of  the  fact  to  the 
foreman,  before  beginning  work;  and  such  men 
should  never  be  assigned  to  difficult  duties,  nor  to 
any  kind  of  work  the  natural  and  inevitable  hazard 
of  which  would  be  materially  increased  by  reason  of 
their  maladies  or  imperfections. 

Youthful  and  inexperienced  persons,  even  though 
well  and  strong,  should  never  be  assigned  to  work 
requiring  skill  and  sound  judgment.  In  dealing  with 
foreigners,  see  that  they  clearly  understand  the  orders 
they  receive,  and  the  dangers  to  which  they  are 
exposed. 

The  safety  spirit  should  be  instilled  into  the  minds 
of  the  men  in  every  way  possible.  They  should  be 
made  to  understand  that  their  own  safety  is  desired 
above  all  else,  and  that  precautionary  measures  that 
are  taken  by  the  employer  or  the  foremen  must 
necessarily  fail  to  be  wholly  effective  unless  the  men 
are  willing  to  co-operate  in  all  possible  ways.  Every 
man  should  be  encouraged  to  report  any  defect  he  may 
discover,  and  to  make  any  reasonable  suggestion  that 
may  occur  to  him  for  securing  greater  safety. 


THE  HUMAN  ELEMENT  317 

Wrestling,  scuffling,  ' 'horse-play",  or  the  playing 
of  so-called  practical  jokes,  should  never  be  permitted 
about  a  scaffold  nor  about  any  part  of  a  building  in 
course  of  construction;  and  no  workman  should  be 
allowed  to  climb  or  slide  upon  ropes,  chains,  or  poles, 
nor  to  ride  on  loads,  nor  upon  material  hoists  of  any 
kind.  There  should  be  no  unnecessary  shouting 
or  other  loud  or  disturbing  noises  in  the  vicinity  of 
the  scaffold.  See  that  everything  is  done  in  a  dignified, 
seemly  way,  so  that  the  workmen  may  be  in  complete 
possession  of  all  their  faculties,  at  all  times. 

Never  allow  a  workman  to  expose  himself  to 
unnecessary  danger,  nor  to  cause  any  of  his  fellow 
workmen  to  be  exposed  to  such  danger.  Men  some- 
times expose  themselves  purposely  in  this  way,  appar- 
ently to  impress  their  associates  with  their  coolness 
and  indifference.  This  tendency  should  be  firmly 
repressed.  The  unavoidable  hazards  are  quite  large 
enough,  and  there  is  no  need  of  wilfully  increasing 
them. 

Nothing  should  be  thrown  down  from  a  scaffold 
without  the  express  permission  of  the  foreman,  who 
must  never  give  such  permission  without  taking  every 
necessary  precaution  to  see  that  nobody  is  exposed 
to  danger.  (Compare  paragraph  159.) 

Do  not  let  the  men  throw  things  down  upon  the 
scaffold  platform,  and  do  not  let  the  men  themselves 
jump  down  upon  the  platform  from  a  higher  level. 
(See  paragraph  127.) 

Men  who  work  upon  scaffolds  or  in  other  elevated 
places  should  avoid  the  use  of  alcoholic  drinks  of  any 
kind,  during  working  hours  or  before  them.  Intoxi- 
cated men  should  never  be  permitted  to  work  upon  a 


318  GENERAL  COUNSEL 

scaffold,  nor  even  to  loiter  about  the  workplace.  This 
rule  should  be  enforced  not  only  against  men  who  are 
uncertain  in  their  movements  or  disposed  to  give 
trouble,  but  also  against  all  who  show  signs  of  intox- 
ication even  in  the  slightest  degree.  The  handling 
of  cases  of  this  kind  is  often  a  delicate  matter,  but  the 
foreman  should  be  firm  and  should  make  it  plain  that 
his  action  is  prompted  solely  by  his  interest  in  the 
safety  of  the  men,  and  not  by  any  desire  to  give  offense. 

155.  Inspection  and  Supervision.  No  scaffold 
should  be  used  by  the  workmen,  nor  should  any 
material  be  lodged  upon  it,  until  all  the  work  of  con- 
struction has  been  completed,  including  the  installation 
of  the  bracing  and  the  erection  of  the  hand-rails, 
foot -boards,  and  other  protective  devices.  The  tempta- 
tion to  work  upon  an  unfinished  scaffold  is  often  very 
considerable,  owing  to  the  work  being  in  a  backward 
state,  or  to  the  offering  of  a  large  bonus  for  haste,  or 
to  the  need  of  closing  in  the  walls  during  the  con- 
tinuance of  favorable  weather,  or  for  some  other 
strong  reason.  It  should  never  be  done,  however, 
because  the  disadvantages  are  likely  to  greatly  out- 
weigh the  supposed  advantages. 

Every  scaffold  should  be  carefully  inspected  by  a 
competent  man,  after  it  is  completed  and  before  it  is 
used.  This  is  essential  even  when  the  scaffold  is  of 
relatively  small  importance  and  is  to  be  used  for  a  very 
brief  time,  because  structures  of  this  kind,  that  are 
to  be  used  only  for  a  few  hours  or  a  few  days,  are  par- 
ticularly likely  to  be  erected  without  due  regard  to 
safety.  Fig.  125  illustrates  this  fact.  The  plank  there 
shown  was  laid  down  to  stand  on,  while  doing  some 
work  on  the  iron  stack;  but  instead  of  providing  a 


INSPECTION  AND  SUPERVISION 


319 


proper  support  for  it,  the  workman  propped  up  one 
end  by  means  of  a  shaky  combination  of  two  tiles 
and  an  inverted  mortar  box. 

A  far  more  striking  example  of  carelessness  and 
indifference  is  illustrated  in  Fig.  126,  which  shows  a 
riveters'  scaffold  that  was  erected  for  use  in  the  con- 
struction of  a  modern  steel-framed  building.  These 
scaffolds  are  used  for  only  a  short  time,  and  they  are 
often  put  up  with  correspondingly  little  care.  In  this 


FIG.  125.     AN  EXAMPLE  OF  CARELESSNESS. 

case  the  wooden  piece  that  was  used  for  the  needle- 
beam,  and  which  is  indicated  at  A,  was  not  long 
enough  to  serve  its  purpose  properly,  and  it  was 
therefore  pieced  out  by  the  steel-workers  in  a  peculiar 
manner,  by  means  of  a  couple  of  blocks  of  wood  of 
the  same  thickness  as  the  needle-beam,  and  a  pair  of 
thin,  weak  side-strips  to  hold  them  in  place,  as  is 
plainly  shown  in  the  illustration.  This  construction 
would  be  hazardous  enough,  even  if  the  material  were 
sound;  but  to  make  the  case  worse  the  side-piece 


GENERAL  COUNSEL 


FIG.  126.     A  DANGEROUS  MEEDLE-BEAM  SCAFFOLD. 

(Erected  for  use  by  a  gang  of  riveters  on  a  large  office  building.  Note  the  weak  section 
at  B.  This  condition  was  discovered  by  a  TRAVELERS  inspector,  who  reported  it  to  the 
superintendent  of  the  job  and  had  the  structure  condemned  before  the  riveters  could  use  it.) 


INSPECTION  AND  SUPERVISION  321 

facing  the  observer  had  a  very  bad  knot  in  it  directly 
opposite  the  point  B.  It  may  be  of  interest  to  state 
that  this  construction  was  detected  by  a  TRAVELERS 
inspector  very  soon  after  the  scaffold  was  placed  in. 
position,  and  was  promptly  condemned  before  it  could 
cause  an  accident. 

Examples  of  carelessness  similar  to  those  shown 
above  are  to  be  seen  everywhere  on  construction  jobs, 
and  they  contribute  greatly  to  the  accidents  that  occur 
in  connection  with  such  work.  They  are  also  common 
in  many  other  places. 

It  should  be  the  duty  of  some  specified  person 
to  keep  a  general  watch  over  every  scaffold,  large  or 
small,  during  the  entire  period  that  it  is  in  use.  The 
man  to  whom  this  duty  is  assigned  should  be  con- 
stantly on  the  watch  for  thoughtless  and  careless  work 
such  as  we  have  described  above,  and  he  should  also 
inspect  every  scaffold  thoroughly  at  least  once  a  day, 
to  see  that  it  is  constantly  maintained  in  a  good, 
safe  condition.  The  best  time  to  make  the  inspection 
is  in  the  morning,  before  the  men  are  at  work.  The 
supervision  should  be  particularly  careful  and  searching 
when  the  conditions  are  such  that  the  failure  of  the 
structure  would  be  likely  to  endanger  a  considerable 
number  of  persons,  whether  they  are  workmen  or  not. 
The  inspector  should  examine  the  various  fastenings 
to  see  that  they  have  not  become  loosened,  and  he 
should  also  give  close  attention  to  the  supports, 
braces,  suspension  cables,  ropes,  clamps,  putlogs, 
bearer-bars,  platform  planks,  guard-rails,  ladders,  and 
all  other  parts  that  are  essential  to  strength  and  safety ; 
and  when  inspecting  a  bricklayers'  pole  scaffold  he 
should  be  particularly  careful  to  see  that  the  putlogs 


322  GENERAL  COUNSEL 

rest  in  the  proper  manner  in  the  holes  provided  for 
them  in  the  wall. 

It  is  an  excellent  plan  to  have  a  special  inspection 
of  every  large  scaffold  made  once  a  week,  in  addition  to 
the  daily  inspections  here  recommended.  After  every 
special  inspection  of  this  kind,  a  written  and  signed  re- 
port should  be  submitted  to  the  superintendent,  in 
which  a  definite  statement  is  made  with  regard  to  the 
condition  of  every  important  element  of  the  scaffold. 

Work  upon  scaffolds  should  be  discontinued  during 
severe  storms  and  high  winds,  and  after  every  such 
storm  or  wind  the  scaffolds  should  be  thoroughly 
inspected  in  every  detail,  and  any  damage  that  has 
been  done  should  promptly  be  made  good.  In  making 
an  inspection  after  a  storm  it  should  be  remembered 
that  planks  and  other  wooden  parts  swell  when  they 
become  wet,  and  care  should  be  taken  to  see  that  no 
damage  has  been  done  to  the  scaffold  from  this  cause. 

In  wintry  weather  scaffold  planks,  ladders,  run- 
ways, and  other  surfaces  where  men  must  step  or  loads 
must  be  deposited,  often  glaze  over  with  ice  or  frost 
so  as  to  become  exceedingly  slippery.  All  such  sur- 
faces should  be  liberally  sprinkled  with  sand  or  ashes 
or  some  equivalent  material,  before  the  men  are 
allowed  to  use  them.  The  upper  surfaces  of  walls 
upon  which  beams  and  other  heavy  objects  are  to 
rest  temporarily  should  also  be  treated  in  the  same  way. 

The  great  importance  of  overhead  protection, 
and  of  guard-rails,  foot -boards,  and  side  screens,  is 
evident  from  the  fact  that  in  a  large  proportion  of 
cases  the  accidents  that  occur  are  due  either  to  the 
falling  of  the  men  themselves,  or  to  the  fall  of  tools  or 
materials  upon  men  who  are  working  or  passing 


INSPECTION  AND  SUPERVISION  323 

below.  Special  attention  should  be  paid  to  safeguards 
of  this  kind,  and  they  should  be  kept  in  first-class  con- 
dition at  all  times. 

Many  accidents  occur  from  the  fall  of  hammers 
and  other  implements  that  are  carried  loosely  in  the 
belts  or  pockets  of  workmen.  The  men  should  not  be 
allowed  to  carry  tools  in  this  way  when  climbing 
ladders,  or  when  working  on  sloping  roofs  or  in  other 
high  places  with  no  protection  but  safety-belts  and 
life-lines. 

Runways  should  preferably  consist  of  an  odd 
number  of  planks,  so  that  a  wheelbarrow  will  "track" 
along  the  middle  of  a  plank,  and  not  along  the  crack 
separating  the  abutting  edges  of  two  contiguous 
ones. 

On  platforms  and  similar  places,  boards  having  a 
thickness  of  1  1/2  inches  or  less  should  not  project  over 
the  beams,  putlogs,  bearer-bars,  brackets,  or  other 
objects  that  support  them,  by  more  than  6  inches;  and 
planks  having  a  thickness  of  2  inches  or  more,  when 
used  in  like  manner,  should  not  project  beyond  their 
supports  by  more  than  12  inches.  This  is  on  the 
assumption  that  the  boards  or  planks  are  not  fastened 
in  any  way.  A  materially  greater  projection  may  of 
course  be  allowed  if  they  are  made  secure  against 
tipping,  by  nails  or  otherwise. 

Take  special  care  with  ladders,  because  they  cause 
a  great  many  accidents.  (See  paragraph  76.)  The 
rungs  should  not  be  loose  enough  to  roll,  and  ladders 
with  missing  rungs  should  not  be  used.  See  that  the 
side-bars  rest  evenly  and  securely  on  a  firm  and  level 
foundation,  and  never  block  them  up  with  bricks, 
tiles,  or  other  similar  objects. 


324  GENERAL  COUNSEL 

See  that  all  hammers,  saws,  axes,  chisels,  and 
other  implements  are  kept  in  safe  places. 

Look  carefully  for  projecting  nails  and  sharp 
splinters,  and  see  that  they  are  removed  at  once,  or 
made  harmless.  (See  paragraph  159.) 

Scaffolds  and  their  approaches,  particularly  in 
connection  with  construction  work,  are  often  used  for 
the  storage  of  tools  and  materials.  This  cannot  be 
wholly  avoided,  in  all  cases,  but  it  is  often  done  to  an 
unreasonable  extent.  Passageways  and  stairways  are 
frequently  used  in  a  similar  way,  with  the  result  that 
they  become  littered  up  so  that  they  are  dangerous  to 
the  workmen.  See  that  obstructions  of  this  kind  are 
reduced  to  a  minimum,  and  do  away  with  them  alto- 
gether whenever  possible. 

On  scaffold  platforms  take  special  care  of  barrels 
and  all  other  objects  that  may  tip  over  or  roll. 

See  that  bottles  containing  gasoline,  muriatic 
acid,  or  other  chemicals  are  plainly  marked,  and  put 
them  in  charge  of  some  one  responsible  man.  Pails 
that  are  used  for  acid  solutions  or  other  poisonous 
substances  should  be  plainly  marked  "POISON",  and 
should  never  be  used  for  any  purpose  other  than  the 
one  for  which  they  were  intended.  In  particular,  they 
should  never  be  left  about  where  they  may  be  mistaken 
by  the  workmen  for  buckets  of  drinking  water. 

Great  care  should  be  taken  in  handling  keystones, 
window  capstones,  and  other  similar  heavy  masses, 
because  serious  accidents  happen  every  little  while 
from  the  fall  of  such  objects  upon  the  platforms  of 
scaffolds. 

Special  precautions  should  be  taken  to  prevent 
ropes  from  becoming  chafed  by  rubbing  against  walls 


INSPECTION  AND  SUPERVISION  325 

or  other  obstacles.  The  suspension  ropes  of  swinging 
scaffolds  should  be  kept  free  from  the  building,  wherever 
necessary,  by  methods  that  will  be  suggested  by  the 
circumstances  of  the  case.  Where  abrasion  is  likely 
to  occur  in  any  other  way,  effective  protection  should 
also  be  provided.  Wrapping  the  rope  with  burlap 
or  with  rags,  or  applying  a  pad  (sometimes  called  a 
"softener")  of  other  soft  material  to  the  object  against 
which  the  rope  rubs,  will  often  afford  satisfactory 
protection.  Never  paint  steel  stacks,  or  other  similar 
objects,  when  they  are  so  hot  as  to  make  it  possible 
that  the  scaffold  ropes  may  be  charred  or  otherwise 
damaged. 

All  ropes,  slings,  and  tackle,  that  are  likely  to  be 
used  for  scaffolds  or  for  hoisting,  should  be  inspected 
with  particular  care,  and  when  not  in  use  they  should 
be  stored  in  a  dry  place,  under  the  charge  of  the 
foreman  or  some  other  specially  designated  person  who 
should  be  held  responsible  for  the  safe  condition  of 
everything  of  the  kind  that  is  given  out  to  the  men. 
Ropes  that  are  considered  to  be  unsafe  should  be 
destroyed,  to  avoid  all  possibility  of  using  them  again 
by  mistake. 

See  that  all  knots  are  securely  tied,  and  wherever 
practicable  lash  the  ends  of  the  rope  with  small  cord, 
close  to  the  knot,  to  prevent  untying. 

Scaffolds  should  always  be  taken  down  as  soon  as 
they  have  fully  served  the  purpose  for  which  they  were 
erected. 

Test  all  swinging  scaffolds  that  are  to  be  used 
for  painting,  cleaning,  decorating,  and  other  similar 
purposes,  by  the  method  recommended  in  paragraph 
147,  under  "Miscellaneous  Scaffolds". 


326  GENERAL  COUNSEL 

156.  Interference  with  Scaffolds.  Whenever 
there  is  even  a  remote  likelihood  of  a  scaffold  being 
wilfully  disturbed,  either  by  the  removal  of  material 
from  it  or  in  any  other  way,  some  one  or  more  specially 
designated  men  should  be  charged  with  the  duty  of 
protecting  it  and  preventing  such  interference.  It 
is  by  no  means  uncommon  for  some  person  needing  a 
piece  of  wood  to  pull  a  promising  section  of  it  from 
a  scaffold  upon  which  men  may  be  at  work;  and  the 
piece  that  is  detached  is  often  essential  to  the  safety 
of  the  men  above,  because  in  building  scaffolds  it  is 
not  customary  to  put  in  any  considerable  amount  of 
unnecessary  material.  We  recall  one  case  in  which 
a  man  removed  a  board  from  a  scaffold,  without 
authority  to  do  so,  and  used  it  to  bridge  a  gap  between 
the  scaffold  and  an  iron  beam  near  by.  The  board 
broke  while  the  man  was  standing  upon  it,  and  as  he 
was  injured  by  the  fall  he  brought  suit  against  the 
contractor  who  erected  the  scaffold  and  endeavored 
to  collect  damages  to  the  extent  of  five  hundred  dollars. 

The  person  responsible  for  the  safety  of  the  scaffold 
should  see  to  it,  not  only  that  no  part  of  the  structure 
is  removed,  but  also  that  there  is  no  interference  with 
the  scaffold  in  any  way  whatsoever.  The  importance 
of  this  advice  is  well  shown  by  the  following  experience 
with  a  high,  fixed  scaffold  in  the  very  heart  of  the 
financial  section  of  New  York  City,  where  the  travel 
is  heavy  and  the  sidewalk  and  street  are  often  badly 
congested.  The  scaffold  was  well  constructed,  and 
upon  it  there  rested  a  total  load  of  nearly  one  hundred 
tons,  consisting  of  stone,  mortar,  water  barrels,  and 
various  other  things,  in  addition  to  the  many  workmen. 
A  gang  of  pipe -fitters  on  the  ground  level,  wishing  to 


INTERFERENCE  WITH  SCAFFOLDS  327 

bend  some  pipe  and  not  being  provided  with  the 
proper  tools,  bored  holes  through  the  uprights  of 
the  scaffold  to  hold  the  ends  of  the  pipe.  The  bending 
was  then  done  by  forcing  the  free  end  of  the  pipe  in  a 
horizontal  direction,  as  though  trying  to  wrap  it  around 
the  pole.  A  severe  twisting  stress  was  thereby  thrown 
upon  the  poles,  and  the  holes  also  became  splintered 
and  ragged  in  a  short  time,  so  that  it  soon  became 
necessary  to  bore  new  ones.  By  this  process  the 
scaffold  was  seriously  weakened  before  the  man  in 
charge  of  it  observed  what  the  pipe-fitters  were  doing, 
but  the  danger  was  fortunately  detected  before  an 
accident  occurred.  The  damage  was  repaired,  and 
thereafter  a  watch  was  set  at  the  base  of  the  scaffold, 
to  see  that  nobody  tampered  with  it  further. 

One  more  illustration  of  the  danger  of  interfering 
with  a  scaffold  may  perhaps  be  given  with  advantage. 
In  this  case  a  number  of  men  were  constructing  a  gas 
tank,  and  three  of  them  were  working  on  a  scaffold 
consisting  of  a  twelve-inch  plank  resting  upon  brackets 
that  were  fastened  to  the  outside  of  the  tank.  There 
were  supposed  to  be  two  bolts  .to  each  bracket, — one 
at  the  top  and  one  at  the  bottom ;  but  when  the 
scaffold  was  put  up  the  bottom  hole  of  one  of  the 
brackets  did  not  come  in  line  with  any  of  the  holes  in 
the  outside  of  the  tank,  and  consequently  no  bolt 
was  put  in  at  this  particular  place.  At  the  time  of 
the  accident  the  men  were  working  on  the  sixth  course 
of  the  tank,  counting  from  the  ground.  A  gang 
of  riveters,  working  on  the  inside  of  the  tank  at  the 
same  level,  started  to  remove  the  nut  from  the  single 
bolt  that  held  up  the  bracket  that  was  supporting  the 
men  on  the  outside.  Somebody  called  to  them  and 


328  GENERAL  COUNSEL 

asked  if  they  were  not  removing  the  wrong  bolt ; 
but  for  some  reason  they  continued  to  take  the  nut 
off,  and  then  struck  the  bolt  from  the  inside  with  a 
maul.  The  scaffold  fell  immediately.  One  of  the 
workmen  was  fatally  injured,  another  had  his  shoulder 
dislocated,  and  a  third  had  two  bones  broken  in  his 
foot  and  one  rib  fractured. 

In  addition  to  interference  consisting  in  voluntary 
though  rarely  malicious  acts  such  as  we  have  described 
above,  there  are  other  ways  in  which  scaffolds  may 
be  disturbed  with  equally  disastrous  effects,  but  with- 
out intention  on  the  part  of  any  person.  For  example, 
a  wagon  may  weaken  the  pole  of  a  scaffold  by  backing 
up  against  it  or  colliding  with  it,  or  by  dumping 
a  heavy  mass  of  material  against  it ;  or  swinging  loads 
may  come  into  collision  with  the  poles,  platforms,  sus- 
pension cables,  or  other  parts  of  the  scaffold.  The 
results  of  an  accident  of  this  kind  are  shown  in  Fig. 
127,  which  shows  the  remains  of  a  horse  scaffold. 
A  slack  hoisting  rope  became  accidentally  looped  under 
some  projecting  part  of  this  scaffold,  and  when  the 
hoisting  signal  was  given  the  scaffold  was  immediately 
reduced  to  the  condition  shown  in  the  engraving. 

When  a  scaffold  is  used  at  or  near  a  place  where 
hoisting  is  done,  projecting  parts  of  it  are  likely  to  be 
caught  or  struck  by  the  objects  that  are  being  hoisted, 
or  by  the  hoisting  tackle  itself.  This  danger  should 
be  constantly  remembered,  and  although  it  is  necessary 
for  the  putlogs  or  bearer-bars  of  fixed  scaffolds  to 
project  outward  to  some  extent,  the  possibility  of 
loads  catching  upon  them  should  never  be  forgotten, 
and  the  operation  should  be  conducted  with  corres- 
ponding forethought  and  caution.  Special  care  must 


INTERFERENCE  WITH  SCAFFOLDS  329 


FIG.  127.     REMAINS  OF  A  HORSE  SCAFFOLD,  AFTER  IT  HAD  BEEN 
FOULED  BY  A  HOISTING  CABLE. 


330  GENERAL  COUNSEL 

also  be  taken  to  safeguard  scaffolds  standing  near  rail- 
road tracks,  roadways,  or  passageways  of  any  kind 
where  heavy  teaming  is  likely  to  be  done. 

It  is  impossible  to  discuss  all  the  sources  of  danger 
to  which  scaffolds  are  subject.  Their  number  is  legion, 
and  they  are  often  easy  to  overlook.  In  one  case 
that  came  to  our  notice,  a  steel  suspension  cable  acci- 
dentally came  in  contact,  high  overhead,  with  a  wire 
conveying  electricity  at  a  considerable  tension.  The 
chafing  that  followed  rubbed  the  insulation  from  the 
electric  wire,  and  occasional  short-circuiting  occurred 
between  the  conductor  and  the  cable,  with  the  result- 
ing formation  of  electric  arcs  that  had  burned  the  cable 
about  half  off  before  the  danger  was  detected. 

In  every  case  in  which  there  is  reason  to  think 
that  the  scaffold  may  be  subject  to  interference  or  dis- 
turbance of  any  kind,  either  intentional  or  purely 
accidental,  a  watchman  should  be  posted  at  some  suit- 
able point  to  protect  the  structure  against  damage 
and  insure  its  integrity. 

157.  The  Load  on  the  Platform.  As  we  have 
repeatedly  said  in  the  course  of  this  volume,  it  is  of 
the  highest  importance,  in  every  form  of  scaffold, 
to  avoid  overloading  the  platforms.  They  should  not 
be  used  for  the  storage  of  materials  that  are  either 
heavy  or  bulky, — excessive  weight  being  manifestly 
dangerous  by  reason  of  the  severe  stresses  thrown 
upon  the  parts,  and  unreasonable  occupation  of  space 
by  bulky  objects  being  also  dangerous  by  reason  of 
the  obstruction  that  is  thereby  offered  to  the  free 
travel  of  the  workmen.  Material  should  never  be 
deposited  upon  the  platforms  faster  than  the  needs 
of  the  workmen  require,  and  the  load  should  always 


LIGHT  331 

be  distributed  over  the  platform  in  a  reasonable  man- 
ner, and  not  concentrated  at  a  few  points. 

Helpers  should  never  be  allowed  to  throw  bricks, 
mortar,  or  other  materials,  down  upon  the  platform 
from  their  shoulders,  because  the  shock  transmitted 
to  the  scaffold  by  so  doing  is  likely  to  lead  to  a  serious 
accident. 

158.  Light.  Work  should  be  done  by  daylight 
only,  whenever  this  is  possible.  If  artificial  light 
must  be  used,  it  should  be  strong  enough  and  pene- 
trating enough  to  enable  the  workmen  to  see  easily  and 
distinctly.  It  should  also  be  diffuse  and  uniform,  and 
should  never  be  localized  in  blinding  centers  of  great 
intensity,  with  comparatively  dark  spaces  between. 
Incandescent  electric  lamps,  proper  in  size  and  number, 
properly  installed  and  distributed,  and  equipped  with 
suitable  reflectors,  are  preferable  to  arc-lamps,  unless 
the  arc-lamps  are  numerous  and  are  arranged  so  as  to 
avoid  strong,  sharp  shadows.  Arc-lamps  that  are  opera- 
ted upon  alternating -current  circuits  of  low  frequency 
are  especially  objectionable,  because  the  light  that 
they  yield  is  usually  intermittent,  with  a  period  equal 
to  that  of  the  electric  current  itself.  This  fact  is  not 
perceived  when  the  eye  is  directed  steadily  toward  one 
object  and  everything  in  the  field  of  view  is  stationary, 
but  it  becomes  immediately  perceptible  whenever  the 
object  or  the  eye  moves  quickly.  A  swinging  hammer, 
for  example,  presents  a  strange  appearance,  suggestive 
of  the  slats  of  a  chicken  coop;  and  the  workman, 
when  his  eye  turns  quickly  from  one  direction  to 
another,  often  experiences  a  peculiar  feeling  which 
is  not  easily  described,  but  which  is  akin  to  dizziness, 
and  tends  to  make  him  uncertain  on  his  feet. 


332  GENERAL  COUNSEL 

Whenever  artificial  light  is  used,  all  ladders, 
stairways,  runways,  and  other  passages  should  be 
especially  well  illuminated.  Workmen  should  be 
forbidden,  under  all  circumstances,  to  step  upon  any 
part  of  the  structure  that  is  not  well  lighted,  or  to 
visit  the  workplace  in  the  dark,  or  to  continue  at  work 
after  the  daylight  has  faded  into  twilight,  unless 
adequate  artificial  illumination  has  been  provided. 

All  electric  wires  that  occur  about  a  scaffold,  in 
connection  with  lighting  or  power  circuits,  should  be 
carefully  and  thoroughly  insulated,  and  they  should 
be  run  in  strict  conformity  with  all  the  laws,  ordinances, 
and  underwriters'  regulations  that  may  be  applicable 
to  them.  The  running  of  electric  wires  is  a  subject 
that  calls  for  special  knowledge  and  training,  and 
it  is  easy  for  an  inexperienced  man  to  violate  condi- 
tions that  are  essential  to  safety. 

159.  Dismantling  Scaffolds.  The  proper  methods 
for  taking  down  suspended  scaffolds  that  are  used  for 
construction  purposes  have  been  described  in  para- 
graphs 109  and  121.  Pole  scaffolds  should  betaken 
down  piece  by  piece,  beginning  at  the  top  and  working 
downward  in  such  a  way  as  to  leave  all  braces,  rails, 
foot -boards,  and  other  safety  features  in  position  until 
they  are  no  longer  needed  for  the  strengthening  of 
the  part  of  the  scaffold  that  remains,  or  for  the  pro- 
tection of  the  workmen.  The  men  should  take  special 
care  to  avoid  falling  when  dismantling  the  scaffold, 
and  also  to  avoid  exposure  to  injury  from  falling 
materials.  In  general,  the  material  that  is  to  be 
removed  should  be  lowered  to  the  ground  on  hoists 
or  by  rope  slings,  and  not  thrown  down.  It  may 
be  permissible,  in  special  cases,  to  throw  down  certain 


DISMANTLING  SCAFFOLDS  333 

parts  of  the  scaffold,  but  no  workman  should  do  this 
without  special  permission  from  the  foreman,  nor 
until  he  has  first  made  sure  that  there  is  no  possibility 
of  injury  to  any  person  below.  It  is  not  enough  for  the 
man  above  to  satisfy  himself  that  no  person  is  in  sight, 
because  it  is  quite  possible  that  somebody  is  in  the 
very  act  of  coming  out  of  a  doorway  or  around  a 
corner  or  from  under  a  shed,  into  the  zone  of  danger. 
To  guard  against  a  contingency  of  this  kind  the  work- 
man above  should  first  look  down  to  see  that  the 
region  of  danger  is  clear,  and  he  should  then  utter  a 
warning  cry,  loudly  and  distinctly,  several  seconds 
before  releasing  his  load.  The  common  habit  of  calling 
out  at  the  very  instant  the  mass  is  thrown  is  ineffec- 
tive and  dangerous.  If  any  considerable  amount  of 
material  is  to  be  thrown  down  in  this  way,  a  watchman 
should  be  stationed  where  he  can  see  and  control  the 
whole  operation.  Although  it  is  defensible  to  throw 
down  certain  materials  when  precautions  similar  to 
those  here  outlined  have  been  taken,  we  desire  to 
strongly  emphasize  the  fact  that  it  is  far  safer  to  lower 
the  materials  on  hoists  or  by  rope  slings  in  all  cases, 
than  to  throw  any  of  them  down;  and  throwing 
should  never  be  permitted,  under  any  circumstances 
whatever,  except  from  very  moderate  heights.  Planks 
and  other  wooden  parts  are  often  badly  damaged  by 
being  thrown  to  the  ground  from  a  scaffold,  and  the 
practice  is  therefore  costly  as  well  as  hazardous. 

In  separating  the  various  members  of  the  scaffold, 
care  should  be  taken  to  avoid  splitting  the  material, 
or  damaging  it  to  an  unnecessary  extent  in  other  ways, 
because  it  may  be  subsequently  needed  on  another 
job,  and  in  that  case  it  should  be  kept  in  as  good  a 


334  GENERAL  COUNSEL 

condition  as  possible.  The  use  of  the  implement 
shown  in  Fig.  11  is  strongly  advised,  when  removing 
ledgers  that  have  been  nailed  to  the  poles. 

When  a  scaffold  is  broken  up,  all  of  its  parts  should 
be  carefully  examined,  at  once,  for  projecting  nails; 
and  any  nails  that  are  found  should  be  drawn  out, 
driven  in,  or  bent  over  in  a  workmanlike  way  so  that 
their  points  are  buried  in  the  wood,  and  so  that 
they  cannot  subsequently  give  rise  to  injuries  in  hand- 
ling the  material,  nor  in  stepping  or  falling  upon  it. 
This  precaution,  though  simple  and  evidently  sensible, 
is  commonly  neglected,  and  ledgers,  braces,  and 
other  parts  of  scaffolds  are  allowed  to  lie  about  with 
nails  projecting  from  them,  menacing  the  workmen. 
Many  injuries  result,  and  some  of  them  are  followed 
by  blood-poisoning  or  other  forms  of  infection,  with 
serious  consequences. 

160.  Scaffolds  Serving  Several  Purposes.  It  often 
happens  that  a  scaffold  is  needed  in  some  given  place 
for  several  successive  kinds  of  work,  to  be  executed 
by  as  many  different  sets  or  "gangs"  of  workmen. 
In  finishing  the  interior  of  a  room,  for  example,  the 
carpenters  and  builders  may  have  need  of  a  scaffold, 
and  later,  in  the  same  room,  the  plasterers  may  need 
one,  and  still  later  the  painters  and  decorators  may 
have  occasion  to  use  one.  In  such  cases  it  is  often  a 
fair  question  whether  the  same  scaffold  should  be  used 
for  all  the  work  that  must  be  done  in  the  given  place, 
or  whether  a  new  and  wholly  different  scaffold  should 
be  built  in  each  case,  by  the  particular  set  of  men 
that  are  to  use  it. 

The  problem  is  somewhat  simplified  if  the  work 
is  all  done  under  one  contractor,  but  even  in  that 


SCAFFOLDS  SERVING  SEVERAL  PURPOSES  335 

case  it  may  not  be  entirely  solved,  because  the  needs 
of  the  different  gangs  of  men  may  be  so  different  that 
one  single  scaffold  will  not  serve  satisfactorily  for 
them  all.  A  bricklayers'  pole  scaffold,  for  example, 
in  which  the  working  platform  is  shifted  to  higher  and 
higher  levels  as  the  work  proceeds,  would  not  be 
adapted  to  any  subsequent  purpose  in  which  constant 
access  to  all  parts  of  the  wall  is  important.  Further- 
more, the  foreman  of  the  first  gang  might  not  thor- 
oughly understand  the  needs  of  the  second  gang, 
and  hence,  even  though  he  were  quite  willing  to  build 
a  scaffold  that  would  serve  all  purposes,  he  might 
fail  on  account  of  his  limited  knowledge.  It  is  also 
possible  that  he  might  not  even  know,  when  building 
the  scaffold,  that  it  was  to  be  used  subsequently 
for  a  different  purpose;  and  in  such  a  case  it  would 
hardly  be  fair  to  shoulder  him  with  a  responsibility 
of  which  he  knew  nothing,  and  which,  if  he  were 
aware  of  it,  he  would  perhaps  be  unwilling  to  assume. 
When  two  or  more  independent  contractors  use 
the  same  scaffold  in  succession,  there  are  many  pos- 
sibilities of  misunderstanding  and  trouble,  and  even 
of  actual  physical  danger  to  the  men.  In  such  a 
case  it  would  not  be  fair  to  the  first  contractor  to 
require  him,  without  special  compensation,  to  go  to 
extra  expense  in  order  to  build  his  scaffold  so  that  it 
would  be  appropriate  to  the  uses  of  others  besides  his 
own  men;  nor  would  it  be  fair,  without  such  compen- 
sation, to  require  him,  after  completing  his  own 
work  and  withdrawing  his  men,  to  keep  the  scaffold 
in  repair  for  his  successors.  Yet  if  the  structure  were 
allowed  to  deteriorate,  the  employees  of  the  second 
contractor,  even  though  forbidden  to  do  so,  might 


336  GENERAL  COUNSEL 

use  it  before  it  had  been  put  in  safe  condition  again, 
and  be  thereby  exposed  to  danger. 

For  these  reasons  among  others,  many  builders 
and  contractors  maintain  that  as  soon  as  one  set  of 
men  has  finished  its  own  special  work,  all  scaffolding 
that  may  have  been  erected  for  the  furtherance 
of  this  work  should  be  pulled  down,  and  that  the 
next  set  of  men  who  have  occasion  to  do  work  in  this 
place  should  build  a  new  scaffold,  adapted  to  their 
own  purposes.  This  involves  a  considerable  extra 
expense,  and  in  most  cases  it  should  be  possible  for 
the  various  contractors  to  combine  their  interests  in 
some  way,  so  that  useless  expenditure  and  loss  of 
time  would  be  avoided  without  sacrificing  the  interests 
of  any  person,  and  without  exposing  the  workmen  to 
unnecessary  danger.  If  the  second  contractor  needs 
a  heavier  and  stronger  scaffold  than  the  first  one,  or 
needs  special  platforms,  or  hoistways,  or  other  features 
that  the  first  one  does  not  use,  these  could  be  pro- 
vided either  at  the  outset  or  later  on, — a  fair  and 
amicable  agreement  being  made  before  beginning  the 
work,  with  regard  to  the  assessment  of  the  costs. 

An  arrangement  of  this  kind  is  likely  to  be  con- 
ducive to  safety  in  more  ways  than  one.  For  example, 
one  of  the  interested  contractors  may  be  a  more 
careful  man  than  another,  and  in  making  arrange- 
ments for  the  building  of  a  scaffold  to  be  used  in 
common,  the  influence  of  the  careful  man,  although 
exerted  primarily  for  the  protection  of  his  own  men, 
will  also  tend  to  increase  the  safety  of  all  other  men 
who  may  use  the  scaffold.  Another  advantage  of 
having  an  understanding  of  this  kind  is  perhaps  worthy 
of  mention.  If,  for  example,  the  scaffold  is  needed 


SCAFFOLDS  SERVING  SEVERAL  PURPOSES  337 

by  the  first  contractor  for  the  actual  performance  of 
work,  while  the  second  one  needs  it  merely  as  a  pro- 
tective precaution  or  safeguard,  there  is  danger  that 
the  second  contractor  might  overlook  it,  or  decline 
to  put  it  up  on  account  of  the  expense  or  the  delay 
that  would  be  involved, — whereas  he  might  be  quite 
willing  to  pay  a  reasonable  amount  for  having  it 
left  in  place,  and  his  men  would  thereby  have  the 
advantage  of  greater  security  than  they  would  have 
had  if  the  separate-scaffold  plan  were  followed. 

In  any  event,  when  a  scaffold  that  has  been  erected 
by  one  set  of  men  for  one  purpose  is  to  be  subsequently 
used  by  another  set  of  men  for  another  purpose,  the 
change  should  never  be  permitted  until  the  foreman 
or  superintendent  of  the  second  crew  has  stated, 
explicitly  and  preferably  before  witnesses,  that  he 
has  carefully  examined  the  scaffold  or  had  it  examined 
by  a  competent  man  under  his  charge,  and  that  he 
is  fully  satisfied  as  to  its  safety.  Furthermore,  in 
case  two  or  more  crews  of  men,  who  are  engaged  on 
different  tasks  under  different  contractors,  have  to 
make  use  of  the  same  scaffold  simultaneously,  the 
foreman  of  each  crew  should  be  required  to  examine 
the  scaffold  and  satisfy  himself  as  to  its  safety  and  its 
adaptability  to  his  purposes,  before  allowing  his  men 
to  use  it.  Under  all  circumstances,  too,  there  should 
be  a  definite  and  unequivocal  agreement  as  to  the 
inspection  of  the  scaffold  and  the  making  of  necessary 
repairs,  and  the  responsibility  for  these  matters 
should  be  fixed  beyond  the  possibility  of  misunder- 
standing or  disagreement,  whether  the  various  crews 
of  men  are  to  use  the  scaffold  simultaneously  or 
successively. 


338  GENERAL  COUNSEL 

161.  Emergencies.  At  every  place  where  a  scaf- 
fold is  used  under  circumstances  that  might  lead  to 
injuries  to  the  workmen,  there  should  be  a  first-aid 
outfit,  containing  supplies  sufficient  to  treat  minor 
injuries.  On  every  large  construction  job  there  should 
also  be  at  least  one  man  who  has  a  thorough  knowledge 
of  the  proper  methods  for  rendering  first-aid  to  the 
injured,  and  he  should  be  supplied  with  a  more  exten- 
sive outfit.  It  is  important,  in  rendering  first-aid, 
to  remember  that  it  is  skill  and  knowledge  that  count, 
and  not  good  intentions.  A  great  deal  of  harm  can  be 
done  by  the  well-meaning  efforts  of  an  uninstructed 
person  in  attempting  to  give  first-aid  to  an  injured 
man,  and  unless  the  service  is  rendered  by  a  man  who 
has  received  thorough  instruction  in  the  art,  it  is 
often  better  to  merely  await  the  arrival  of  a  physician, 
without  attempting  to  render  any  aid  except  to  check 
copious  bleeding  or  to  perform  artificial  respiration. 
It  is  always  better  to  do  something, — even  if  it  is  the 
wrong  thing, — rather  than  to  allow  the  injured  man 
to  die  from  loss  of  blood  or  from  asphyxiation  due 
to  the  cessation  of  his  breathing.  Whenever  a  first- 
aid  cabinet  is  kept  at  hand,  whether  it  is  on  a  con- 
struction job  or  elsewhere,  it  should  be  kept  in  a  dry, 
accessible  place,  and  its  location  should  be  made  known 
to  every  employee,  so  that  it  can  be  found  without  a 
moment  of  unnecessary  delay. 

The  addresses  of  several  physicians  who  can  be 
had  upon  short  notice  should  be  posted  in  some  con- 
spicuous place,  together  with  their  telephone  numbers. 
If  there  is  a  telephone  on  the  job  these  addresses  should 
be  posted  close  to  it,  to  avoid  loss  of  time  in  put- 
ting in  an  emergency  call.  First-aid  services  should 


EMERGENCIES  339 

always  be  regarded  as  just  what  their  name  implies, 
and  in  every  case  of  injury  a  physician  should  be  con- 
sulted as  soon  as  it  is  practicable  to  do  so. 


INDEX. 

(The  references  are  to  pages.    Where  two  or  more  references  are  given  under  the  same  heading, 
black-faced  figures  indicate  the  more  important  ones.) 

Accident  caused  by  improper  handling  of  scaffold  machine,  206. 
from  breaking  of  a  board,  326. 
on  a  gas  tank,  serious,  due  to  carelessness,  327. 
to  a  horse  scaffold,  328. 
Accidents,  scaffold,  exceed  one  a  day,  24. 

general  character  of,  24. 
illustrative  list  of,  13. 
statistics  of,  hard  to  obtain,  11. 
Acids,  danger  to  ropes  from,  268. 

care  of,  324. 
Advice. — See  Counsel. 
Alcohol,  317. 

Alloys.— See  Metals,  fusible. 
Anchor  bolts. — See  Suspended  scaffolds. 
Arch  centers  and  other  false  work,  309. 

Attention  of  scaffold-builder  not  to  be  drawn  away  from  his  work,  315. 
Babbitt. — See  Metals,  fusible. 
Barrels  filled  with  sand  for  scaffold  poles,  44. 
on  scaffold  platforms,  324. 
use  of,  as  supports,  277. 
Beam. — See  Outrigger;   Needle-beam. 
Bearers,  size  of,  and  method  of  nailing,  86. 
for  independent  pole  scaffolds,  93. 
Belts,  safety,  248,  265,  290. 
Bending  moments  on  channel  beams,  200. 
Board,  suit  over  a  broken,  326. 
Boards  of  platforms  not  to  project  beyond  supports,  323. 

— See  also  Planks;    Traps. 
Boatswain's  chair,  34,  289. 
Bolting  high  scaffolds  together,  90. 
Bolts  on  needle-beam  scaffold  planks,  276. 


342  INDEX 

anchor. — See  Suspended  scaffolds. 
— See  Stop  bolt. 
Boston  scaffold,  38. 

Bottles  containing  harmful  substances,  care  of,  324. 
Braces,  material  and  size  of,  73. 
Bracing  for  bricklayers'  pole  scaffold,  70. 
at  window  openings,  74. 
shoring,  75. 
with  spring  stays,  76. 
caution  in  use  of  special  putlogs,  79. 
longitudinal,  80. 

independent  pole  scaffolds,  86,  94. 
lashed  scaffolds,  119. 
horse  scaffolds,  163. 
interior  pole-scaffolds,  282. 
— See  also  Stay-rods. 

Brackets,  iron,  for  supporting  scaffolds,  120. 
carpenters',  258. 
angle,  for  roofs,  262. 

Bricklayers'  pole  scaffold,  general  description  of,  38. 
poles  or  uprights  for,  38. 
ledgers,  47. 
putlogs,  55. 
platforms,  62. 
bracing,  70. 

guard-rails,  foot-boards,  etc.,  82. 
compared  with  independent  pole  scaffold,  84. 
Bricklaying,  general  practice  in,  33. 
"overhand, "  34. 

from  both  sides  of  wall  at  once,  34. 
Bricks. — See  Materials. 
Bridges,  sidewalk. — See  Sidewalk. 
Building  construction,  use  of  scaffolds  in,  33. 
Cables,  "seizing,"  189,  213. 

hoisting,  danger  to  scaffolds  from,  328. 

chains,  and  poles,  men  must  not  slide  down  them,  317. 

suspension,  198. 

securing  by  fusible  metals,  189,  208,  213. 
damage  to,  from  electric  wires,  330. 
material,  size,  and  quality,  212. 
importance  of  having  them  vertical,  193. 
protection  of,  213,  325. 
riding  of,  on  drums,  201,  315. 
securing  to  thrust-outs,  187. 
— See  also  Rope;  Splicing;  Suspended  scaffolds. 
Cantilever. — See  Outrigger. 


INDEX  343 


Canvas. — See  Shields. 
Capstones,  care  in  handling,  324. 
Carelessness,  319. 
Carpenters'  scaffolds,  34,  258. 
Catch-platforms,  137,  257,  264,  299. 
Chain-tightening  device,  114. 
Chains  for  lashing  scaffolds,  114. 

— See  also  Cables;  Rope. 
Chair. — See  Boatswain's  chair. 
Channel  beams,  194. 
Chemicals,  care  of,  324. 
Chestnut  blight,  55. 
Chicken-ladders. — See  Crawling-boards. 
Chimneys,  35,  283. 

— See  also  Stacks. 
Church  spire,  a  scaffolded,  255. 
Clamps  for  securing  ledgers  to  poles,  53,  115. 

— See  also  Clips;   Cramp-irons. 
Cleats  for  foot-holds,  147,  277. 
for  splicing  poles,  46,  91. 
Clips  on  cables,  189. 
Construction  and  material,  312. 
Contractor's  office,  location  of,  298. 
Cords,  wire,  for  lashing,  112. 

Corners,  special  treatment  necessary  at,  49,  60,  67. 
guard-rails  at,  132,  228. 
foot-boards  at,  134,  228. 
Cornice  work,  247. 

irons. — See  Hooks. 

Corrosion  of  cable  ends  from  pickling,  216. 
Counsel,  general,  312. 
Cover-strips  for  scaffold  poles,  46,  91. 
Cradles,  286. 

Cramp-irons,  use  of,  115,  129. 
Crawling-boards,  264,  271. 
Cripples. — See  Brackets. 
Crosby  clips. — See  Clips. 
Cross-bars. — See  Bearers. 
Danger  not  to  be  needlessly  incurred,  317. 
Decorators'  inside  scaffolds,  34,  277,  282. 
Dismantling  suspended  scaffolds,  platform  type,  193. 
overhead  scaffold  machines,  210. 
of  scaffolds  in  general,  152,  332. 
Disturbance  of  scaffolds,  326. 
Doctors,  addresses  of,  to  be  posted,  338. 
Dogs. — See  Cramp-irons. 


344  INDEX 

Drums. — See  Scaffold  machines. 
Duck-ladders. — See  Crawling-boards. 
Education  in  scaffold  construction,  313. 
Electric  wires,  care  of,  332. 

danger  from,  330. 
Emergencies,  338. 
Experience,  need  of,  312. 
Explosion  at  Grand  Central  Station,  172. 
Factor  of  safety  on  outriggers,  253. 

on  ropes,  269,  287,  292. 

Fall  of  men  and  materials,  accidents  from,  322. 
Falls  from  low  elevations,  26. 
False-work  structures,  37,  309. 
Fenders  for  suspended  scaffolds,  218. 
First-aid  outfits,  338. 
Fixed  scaffolds,  27. 
Foot-boards,  82,  98,  132. 

well-arranged,  89. 

seldom  used  on  ladder  scaffolds,  124. 
for  horse  scaffolds,  165. 
for  suspended  scaffolds,  224. 
omitted  when  side  screens  are  used,  226. 
Foreigners  to  receive  special  consideration,  316. 
Foremen  to  examine  scaffolds  for  safety,  314,  337. 

to  see  that  there  is  no  ill  feeling,  315. 
Frost  and  ice,  danger  from,  322. 
Galvanizing  cables,  212. 
Gas  explosion  at  Grand  Central  Station,  172. 

tank  scaffold,  accident  on,  327. 
Gasoline,  care  of,  324. 
Grand  Central  Terminal,  explosion  at,  172. 

interior  scaffold,  104. 
Guard-rails,  82,  98. 

well-arranged,  89,  131. 

for  ladder  scaffolds,  124. 

ledgers  used  as  ,  132. 

at  ends  of  scaffolds,  132. 

material  for,  132. 

on  runways,  147. 

on  stairways,  149. 

on  horse  scaffolds,  165. 

on  suspended  scaffolds,  224. 

on  outrigger  scaffolds,  225. 

on  carpenters'  scaffolds,  261. 

on  needle-beam  scaffolds,  275. 
Guards, — See  also  Watchmen. 


INDEX  345 


Hammers. — See  Tools. 

Hand-rails. — See  Guard-rails. 

Hangers,  painters',  266. 

Haste  in  scaffold-building  is  unwise,  314. 

Heat,  danger  to  ropes  from,  325. 

Hemlock  unsuitable  for  scaffold  construction,  39,  48,  62. 

Hitch  for  securing  painters'  swinging  scaffolds,  267. 

for  needle-beams,  273. 
Hitches. — See  also  Knots. 
Hoists,  material,  304. 

guying  and  bracing,  306. 
to  be  sheathed  inside,  307. 
men  must  not  ride  upon  them,  317. 
Hoisting,  precautions  to  be  observed,  309. 

tackle,  danger  to  scaffolds  from,  328. 

care  of,  325. 

towers. — See  Hoists,  material. 
Hooks  for  holding  suspended  scaffolds  near  wall,  217. 

painters'  scaffolds,  269. 
Horse  scaffolds,  delivering  material  to,  154. 

not  to  be  used  for  heavy  loads,  156. 
platforms  of,  156. 
should  be  limited  in  height,  157. 
insecurely  supported,  159. 
supported  by  thrust-outs,  161. 
shoring  and  bracing,  163. 
ladders  on,  164. 
runways  for,  165. 

guard-rails  and  foot-boards  for,  165. 
protection  of  men  below,  167. 
for  serving  suspended  scaffolds,  219. 
Horses,  use  of,  153. 

design  and  condition  of,  154. 
angle  between  legs,  154. 
to  be  in  good  repair,  155. 
to  be  firmly  supported,  156,  160,  278. 
used  in  tiers,  157,  277. 
to  be  directly  over  one  another,  157. 
for  use  on  independent  pole  scaffolds,  97. 
for  laying  walls  from  the  inside,  153. 
legs  of,  to  be  nailed  down,  161. 
placed  diagonally,  163. 
for  interior  scaffolds,  277. 
extension  of  legs  of,  278. 
Human  element,  the,  315. 
Ice,  danger  from,  322. 


346  INDEX 

Illumination,  331. 
Implements. — See  Tools. 
Independent  pole  scaffold,  83. 

characteristics  of,  83. 
uses  of,  83. 

footing  for  poles  of,  84. 
material  for,  84. 
erected  on  sidewalk  sheds,  84. 
compared  with  bricklayers'  scaffold,  29,  84. 
bracing,  86. 
design  for,  90. 

guard-rails,  foot-boards,  etc.,  98. 
Infirmities  to  be  reported,  316. 
Injuries,  treatment  of,  338. 
Inspection  and  supervision,  249,  318,  321. 
Installing  platform  scaffold  machines,  192. 
overhead  scaffold  machines,  210. 
Interference  with  scaffolds,  326. 
Intoxication,  317. 
Irons. — See  Hangers;  Hooks. 
Jacks.— See  Brackets. 
"Jokes,  practical,"  to  be  forbidden,  317. 
Keystones,  care  in  handling,  324. 
Knots  for  scaffold  lashings,  105. 
security  of,  325. 
—See  also  Hitch. 
Ladder  scaffolds,  35,  123. 

extensively  used  in  foreign  countries,  128. 
Ladders,  141. 

for  independent  pole  scaffolds,  98. 
splicing,  126,  142. 
material  for,  141. 
maximum  length  of,  141. 
extending  above  landings,  141. 
securing  ends  of,  144. 
supporting  at  middle,  144. 
sheathing  underneath,  145. 
regulating  movements  of  men  on,  145. 
on  horse  scaffolds,  164. 
for  supporting  interior  scaffolds,  279. 
iron,  for  climbing  chimneys,  284. 
dangers  from,  323. 
Landslides  and  scaffold  failures,  44. 
Lashed  scaffolds,  99. 

characteristics  of,  99. 

American  and  foreign  practice,  99. 


INDEX  347 

time  and  labor  required  for  erecting,  101. 
use  of  round  wood,  102. 
tying  the  knots,  105. 
splicing  the  uprights,  107. 
fiber  rope  for  lashing,  101. 
wire  cords  for  lashing,  112. 
chains  for  lashing,  114. 
clamps  and  cramp-irons,  115. 
bracing,  119. 

guard-rails  and  foot-boards,  119. 
Lead. — See  Metals,  fusible. 
Ledgers  for  bricklayers'  pole  scaffolds,  47. 
for  independent  pole  scaffolds,  93. 
function  of,  47. 

material,  size,  and  quality,  48. 
relation  of,  to  the  poles,  49. 
arrangement  of,  at  corners,  49. 
vertical  spacing  of,  50. 
erecting,  50. 
nailing,  51. 

testing  security  of,  52. 
splitting  of,  52. 
tool  for  removing,  53,  334. 
clamps  for,  53. 
ratline  used  for  lashing,  101. 
used  as  guard-rails,  132. 
Life  lines,  248,  265,  290. 
Light,  331. 
Loads  on  scaffold  platforms,  330. 

men  must  not  ride  upon  them,  317. 
Machines. — See  Scaffold  machines. 
Manila  rope. — See  Rope. 
Masons'  horse. — See  Horses;   Horse  scaffolds. 

scaffold. — See  Independent  pole  scaffold. 
Materials  for  scaffolds,  quality  of,  38,  48,  55,  62,  90,  149,  253,  260,  273,  313. 

- — See  also  Rope;    Cables;   etc. 

not  to  be  piled  where  they  can  fall  down  upon  a  scaffold,  251. 
delivery  of,  upon  scaffold  platforms,  219,  220,  317,  330. 
throwing  down  from  scaffolds,  317,  332. 
storage  of,  on  scaffolds,  324. 
heavy,  care  in  handling,  324. 
splitting  of,  333. 

Metals,  fusible,  for  securing  the  ends  of  cables,  189,  208,  213. 
Nails  suitable  for  scaffold  work,  51,  149. 
method  of  testing,  151. 
should  be  driven  in  solidly,  152. 


348  INDEX 

and  splinters,  324. 
projecting,  334. 
Needle-beam  scaffolds,  272. 

scaffold,  a  dangerous,  320. 
Netting. — See  Wire  netting. 
Noises,  unnecessary  loud,  to  be  forbidden,  317. 
Office,  contractor's,  location  of,  298. 
Oiling  cable-ends  after  securing  with  fusible  metal,  217. 
Outrigger  scaffolds,  33,  252. 

supervision  of,  258. 
Outriggers,  factor  of  safety  on,  253. 
security  of,  254. 
steel,  255. 

Pails  used  for  acids,  care  of,  324. 
Painters'  scaffolds,  34,  265,  282. 

testing  of,  269,  287. 

care  in  choosing  fellow-workers  on,  271. 
not  to  be  combined,  272. 
number  of  workmen  on,  272. 
— See  also  Decorators. 
Paper-hangers. — See  Decorators. 
Passageways,  protection  over,  137,  257,  299. 

obstruction  of,  324. 
Pawls. — See  Scaffold  machines. 
Physicians,  addresses  of,  to  be  posted,  338. 
Pickling  cable-ends,  216. 
Pinching  of  the  platform  planks,  190,  221. 
Pipes,  use  of  scaffold  poles  for  bending,  326. 
Planks,  platform,  projection  beyond  supports,  323. 

spacing  of,  on  interior  pole  scaffolds,  283. 
on  needle-beam  scaffolds,  security  of,  275. 
safeguard  by  pinching,  190,  221. 
— See  also  Boards;   Materials;  Platforms;    Traps. 
Plasterers'  and  decorators'  inside  scaffolds,  34,  277. 
Platform  of  bricklayers'  pole  scaffold,  62. 

width  of,  63. 

support  of  planking  by  putlogs,  64. 
treatment  of  corners,  67. 
shifting  the,  69. 

planks,  material,  size,  and  quality  of,  62. 
bound  with  hoop-iron,  63. 
not  secured  to  putlogs,  64. 
danger  of  tipping,  64,  156,  260. 
not  to  project  beyond  supports,  323. 
arrangement  of  overlapping  ends,  66. 
at  corners,  67. 


IXDEX  349 

spacing  of,  64,  217,  261,  283. 
safeguarded  by  pinching,  190,  221. 
for  suspended  scaffolds,  218. 

Platforms  of  suspended  scaffolds,  190,  209,  217,  245. 
of  independent  pole  scaffolds,  96. 
of  needle-beam  scaffolds,  security  of,  275. 
of  plasterers'  and  decorators'  inside  scaffolds,  279. 
for  ladder  scaffolds,  126. 
on  horse  scaffolds,  156. 
of  material  hoists,  protective  features,  307. 
auxiliary,  for  serving  suspended  scaffolds,  219. 
for  independent  pole  scaffolds,  304. 
protective,  137,  257,  264,  299,  322. 
double,  for  suspended  scaffolds,  235. 
below  working  platform  of  pole  scaffold,  301. 
load  on,  220,  330. 
— See  also  Traps. 
Poisons,  324. 
Pole  scaffolds,  general  description  of,  27. 

different  methods  of  failure,  71. 
with  iron  supports,  120. 
interior,  279. 
dismantling,  152. 

protection  beneath  working  platforms,  301. 
—See  also  Bricklayers1  pole  scaffold;  Independent  pole  scaffold. 
Poles,  spacing  of,  American  and  foreign  practice,  41. 
scaffold,  setting  lower  ends  of,  43. 
"breaking  joints"  in,  47. 
splicing  of,  45,  91,  107,  282. 
iron,  for  scaffolds,  120. 
use  of,  for  bending  pipes,  326. 
of  bricklayers'  pole  scaffolds,  38. 

material,  quality,  and  size,  38. 
poles  of  extra  strength,  39. 
distance  of  poles  from  wall,  41. 
spacing,  parallel  to  wall,  41. 
bearing  of  pole  at  lower  end,  42. 
landslides  or  slips,  44. 
splicing  and  lengthening,  45. 
for  independent  pole  scaffolds,  91. 
for  lashed  scaffolds,  107. 
for  interior  scaffolds,  282. 

Protection. — See  Foot-boards;    Guard-rails;    Horse  scaffolds;    Platforms,    pro- 
tective;  Shields;   Sidewalk  protection;   etc. 
Putlogs  for  bricklayers'  pole  scaffolds,  55. 
function  of,  55. 


350  INDEX 

American  and  foreign  practice,  55. 
material,  size,  and  quality,  55. 
support  of,  56. 
notching  the  ends  of,  57. 
security  of,  58,  314. 
lashed  with  rope  or  wire  cord,  58. 
location  of,  59. 
treatment  of  corners,  60. 
not  to  be  relied  upon,  for  bracing,  79. 
special  forms  of,  60,  79. 
of  suspended  scaffolds,  190,  209,  218. 
Railings. — See  Guard-rails. 
Ratchet-wheels. — See  Scaffold  machines. 
Ratline  for  lashing  ledger  poles  to  uprights,  101. 
Riding  of  cables. — See  Cables. 
Rollers  on  painters'  scaffolds,  267,  269. 
Roofs,  scaffolds  for,  262. 

corrugated  iron,  scaffolds  for  laying,  287. 
— See  also  Platforms,  protective;   Shields. 
Rope,  standard  hoisting,  212. 

for  use  with  lashed  scaffolds,  101. 
use  of,  for  guard  rails,  131,  224,  275. 
for  needle-beam  scaffolds,  274. 
suspension,  strength  of,  269,  287,  292. 
chafing  of,  324. 
danger  to,  from  acids,  268. 
care  and  protection  of,  325. 
for  supporting  roof  scaffolds,  262. 
use  of,  in  securing  painters'  scaffolds,  270. 
hoisting,  danger  to  scaffolds  from,  328. 
chains,  and  poles,  men  must  not  slide  down  them,  317. 
— See  also  Cables;  Hitch;  Knots. 
Rotting. — See  Acids. 
Running  strips. — See  Ledgers. 
Runways,  145. 

cleats  on,  147. 

remove  ice  and  snow  from,  147. 
hand-rails  on,  147. 

arrangement  of  planks  upon,  147,  323. 
for  horse  scaffolds,  165. 
for  serving  suspended  scaffolds,  220. 

Safeguards. — See   Foot-boards;    Guard-rails;    Pinching;    Shields;    etc. 
Safety,  130,  316. 

features  of  suspended  scaffolds,  194,  211,  224. 

workmen  to  satisfy  themselves  concerning,  315. 

— See  also  Belts;    Cables;    Factor  of  safety;   Foot-boards;   Guard-rails; 


INDEX  351 

Human  element;   Inspection;   Materials;  Platforms,   protective; 
Shields;  Side-walk  protection;  Traps;  Wire  netting;  etc. 
Scaffold  hitch  for  needle-beams,  273. 

for  painters'  scaffolds,  267. 
— See  also  Knots. 
irons. — See  Hangers;  Hooks. 
machines,  platform  type,  176. 

description  of,  176. 
drums  of,  176. 

function  of  ratchet  wheels  of,  177. 
operation  of  machines,  177. 
breakage  of  pawl  or  ratchet-wheel,  179. 
position  of  operating  lever  at  rest,  180. 
disengaging  both  pawls  at  once,  180. 
securing  cables  to  machines,  189. 
putlogs  and  platform,  190. 
pinching  of  platform  planks,  190. 
installing,  192. 
overhead  type,  194. 

general  remarks,  194. 
description  of,  197. 
distribution  of  stress  in,  199. 
effect  of  failure  of  worm-pin,  200. 
riding  of  cables  on  drums,  201,  315. 
precautions  in  leveling  platform,  204. 
insertion  of  worm-pin,  206. 
improper  handling  causes  accident,  206. 
attachment  of  cables  to  drums,  208. 
putlogs  and  platform,  209. 
installing  and  dismantling,  210. 
— See  also  Scaffolds ;  Suspended  scaffolds. 
Scaffolds  for  building,  three  main  classes  of,  27. 
small  hanging,  35. 
for  supporting  hoisting  devices,  36. 
swinging,  to  be  lowered  or  lashed,  269. 

double-platform,  passing  from  one  platform  to  the  other,  237. 
not  to  be  used  until  completed,  318. 
to  be  removed  when  no  longer  needed,  325. 
interference  with,  326. 
serving  several  purposes,  334. 
dismantling  of,  152,  193,  210,  332. 
swinging,  to  be  tested,  269,  287,  325. 
one  over  another,  240. 
miscellaneous,  252,  283. 

— See    also   Arch   centers;     Bricklayers'    pole   scaffold;     Carpenters' 
scaffolds;  Catch  platforms;  Chimneys;  False  work;  Horse  scaf- 


352  INDEX 

folds;    Horses;    Independent    pole  scaffolds;   Ladder  scaffolds; 
Outrigger  scaffolds;  Painters'  scaffolds;  Plasterers'  and  decora- 
tors1 inside  scaffolds;  Pole  scaffolds;  Suspended  scaffolds;  etc. 
Screens,  side,  for  suspended  scaffolds,  224. 
sometimes  required  by  law,  226. 
— See  also  Wire  netting. 
Scuffling. — See  Wrestling. 
Seizing  cables,  189,  213. 

Shackles  for  securing  cables  to  thrust-outs,  187. 
Sheathing,  145,  259,  307. 
Sheds,  sidewalk. — See  Sidewalk. 
Shields  of  canvas  over  platforms  of  suspended  scaffolds,  230. 

necessary  when  one  scaffold  stands  over  another  one,  240. 
of  wood  over  platforms  of  suspended  scaffolds,  233. 
of  wire  netting  for  platforms  of  suspended  scaffolds,  238. 
overhead. — See  Horse  scaffolds;    Platforms,  protective;    Sidewalk  pro- 
tection;  etc. 

Shingling,  scaffolds  used  for,  34,  262. 
Shoring  horse  scaffolds,  163. 
pole  scaffolds,  75. 
interior  scaffolds,  282. 
— See  also  Bracing. 
Sickness  to  be  reported,  316. 
Side  screens. — See  Screens;    Wire  netting. 
Sidewalk  protection,  293. 

sheds  and  bridges,  293. 

used  for  storing  material,  296. 
— See  also  Platforms,  protective. 
Slings.— See  Rope. 

"Softeners"  for  protecting  ropes,  325. 
Soldering  wires  of  wire  netting,  239. 
Splicing  braces  of  independent  pole  scaffolds,  95. 
ledgers  of  independent  pole  scaffolds,  93. 
poles  of  bricklayers'  pole  scaffolds,  45. 
of  independent  pole  scaffolds,  91. 
of  lashed  scaffolds,  107. 
suspension  cables  to  form  eyes,  188,  209. 
Splinters  and  nails,  324. 
Splitting  of  materials,  52,  333. 
Spring  stay  braces,  general  description,  76. 

to  be  set  in  every  putlog  hole,  78. 
— See  also  Bracing. 
Stacks,  iron,  ascending  and  painting,  285. 

— See  also  Chimneys. 
Stagings. — See  Scaffolds. 
Stairways,  97,  149. 


INDEX  353 

Statistics  of  scaffold  accidents  hard  to  obtain,  11. 
Stay-rods  for  iron  scaffold  brackets,  121. 
Step-boards.— See  Crawling-boards. 
Stirrups  for  platform  planks  of  ladder  scaffolds,  126. 

— See  also  Hangers. 
Stone,  scaffolds  for  laying,  29. 

heavy,  care  in  handling,  324. 

Stop  bolt  to  prevent  shackle  from  slipping  from  thrust-out,  188. 
Storage,  use  of  scaffolds  for,  324. 
Storms,  securing  scaffolds  to  resist,  97. 

work  to  be  discontinued  during,  322. 
inspections  after,  322. 

Strap  of  steel  for  inclosing  platform  planks,  221. 
Stresses  in  oyerhead  type  of  scaffold  machine,  199. 
Suit  over  a  broken  board,  326. 

Superintendents  and  foremen  to  see  that  scaffolds  are  safe,  314. 
Supervision  and  inspection,  318. 
Suspended  scaffolds,  general  description  of,  31,  168. 
distinctively  American,  313. 
safety  of,  32,  172. 

and  outrigger  scaffolds,  distinction  between,  33. 
limited  applicability  of,  168. 
advantages  of,  170. 
flexibility  of,  171. 
two  main  types,  173. 
support  of,  174. 

shifting  the  thrust-outs  of,  242. 
platform  type,  definition  of,  174. 

thrust-outs  for  sustaining,  182. 
anchor  bolts  for,  183. 
beam  clamps  for,  185. 
securing  suspension  cables,  187,  189. 
putlogs  and  platform,  190. 
pinching  of  platform  planks,  190. 
installing  the  machines,  192. 
dismantling,  193. 

miscellaneous  safety  features,  194. 
overhead  type,  definition  of,  174. 

location  of  machines,  194. 
thrust-outs  for,  194. 
putlogs  and  platform,  209. 
miscellaneous  safety  features,  211. 
comparison  of  overhead  and  platform  types,  245. 
varied  practice  in  the  United  States,  212. 
protected  from  falling  objects,  229. 
passing  materials  to  platforms,  219. 


354  INDEX 

inspection  of,  249. 
and  cornice  work,  247. 
— See  also  Painters'  scaffolds. 

Suspension  cables. — See  Cables;  Rope;  Suspended  scaffolds. 
Swinging  scaffolds. — See  Suspended  scaffolds;   Painters1  scaffolds. 
Tackle.— See  Rope. 

Tar  used  to  preserve  scaffold  poles,  43. 
Testing  swinging  scaffolds,  269,  287. 

Thrust-outs  for  overhead  type  of  suspended  scaffold,  194. 
special  methods  of  securing,  195. 
for  suspended  scaffolds,  wooden  and  steel,  212. 
of  suspended  scaffolds,  shifting,  242. 
for  supporting  horse  scaffolds,  161. 
— See  also  Outriggers;   Suspended  scaffolds. 
Timber. — See  Materials;    Wood;  etc. 
Toe-boards. — See  Foot-boards. 
Tool  for  removing  ledgers,  53,  334. 
Tools,  danger  from  fall  of,  323. 

to  be  kept  in  safe  places,  324. 
Towers,  hoisting,  304. 
Traps  in  scaffold  platforms,  64,  156,  260. 
Trestles. — See  Horses. 
Uprights. — See  Poles. 
Watchmen,  posting  of,  330,  333. 
Wheels. — See  Rollers. 
Winds. — See  Storms. 
Wire  cords. — See  Cords. 
nails. — See  Nails. 
netting,  135. 

on  independent  pole  scaffolds,  98. 
to  be  used  on  sidewalk  sheds,  137. 
for  overhead  shields  of  suspended  scaffolds,  238. 
for  catch-scaffolds,  301. 
soldering  wires  of,  239. 
— See  also  Screens,  side. 
Wires,  electric,  care  of,  332. 

danger  from,  330. 
Wood,  round,  for  scaffolds,  102. 

Workplaces,  protection  over. — See  Platforms,  protective. 
Worm-pin,  effect  of  failure  of,  200. 

insertion  of,  206. 

Worms. — See  Scaffold  machines,  overhead  type. 
Wrestling  and  scuffling  to  be  forbidden,  317. 
Zinc,  use  of,  in  shingling,  263. 
— See  also  Metals,  fusible. 


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